i MERA PUBLICATIONS. No. 2. The Scientific and Economic Aspects of the Cornish Pilchard Fishery. 2.—The Plankton of the Inshore Waters in 1913 considered in relation to the Fishery. By HAROLD SWITHINBANK, Fellow of the Royal Socisty of Edinburgh, and G. E. BULLEN. ST. ALBANS PRESS, 1914. MERA PUBLICATIONS. No. 2. The Scientific and Economic Aspects of the Cornish Pilchard Fishery. 2.—The Plankton of the Inshore Waters in 1913 considered in relation to the Fishery. By HAROLD SWITHINBANK, Fellow of the Royal Society of Edinburgh, and G. E. BULLEN. ! ST. ALBANS PRESS, 1914. ee ee The Scientific and Economic Aspects of the Cornish Pilchard Fishery. 2.—The Plankton of the Inshore Waters in 1913 considered in relation to the Fishery. By Harorp SwiTHINBANK, F.R.S.E., and G. E. BuLien. Metuops anp Data. The observations upon which the following researches are founded were taken from the s.s. Mera, R.Y.S. during two cruises in the Summer of 1913. ‘The original scheme of work was planned with a view to determining what contrasts existed in the plankton environment (a) between the principal fishing areas, ¢.g., Mevagissey Bay, Mounts Bay and St. Ives Bay, and (4) before and after the inshore migration of pilchards took place. The first of these cruises was undertaken from May 31st to June 3rd. Twelve stations were worked in Mevagissey and St. Austell’s Bays (see Chart.No. 1), eleven in Mounts Bay (see Chart No. 2), and six in St. Ives Bay (see Chart No. 3). Certain full speed tow-nettings were also taken between inter- mediate points. The positions of the several stations, together with surface temperature and other details, are shown in the following table (Table No. 1). 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(AZ Valtupy) swmoyze4—'siu9j + Saajayy—= Su : aN peads [nw y—'S A—SNOILVIAWNA AY “SHILIi II¥S @IVAYNAS ‘SHAALVUAING [, @Ovayns “SONIGNNOS ‘SNOILV.LS HO SNOILISOG ONIMOHG BUEN? LJ] COIN, Grusny jf, OF THE CORNISH PILCHARD FISHERY. os ‘ysupw ZT "M00 Z9°T X'°N 00°84 0G] S 4 tS “ 0€ OI M 00°ST'% XN 00°12'0S] Sa 4 ~ O23 ‘M 00 P'S X N 00'LT 081S 4 “ om O29) ‘M 00°01 € XN OO'FT OS}'S a} e “08°F : : ‘A\ 00 LE°§ XN O0'TI OS|'S'4 “ 08 OR M 00'90'F XN 001 0S]'S 4 4196 "sny|'w'd oe Zr ‘M 00 86°F X N00 LT0S1S 4) PeeH sueqry 15 0} o110djog oe 80. 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The full number of stations was worked in St. Ives Bay; a detour was made to obtain observa- tions at three positions in St. Mary’s Sound, Scilly ; the number of stations in Mounts Bay and Mevagissey Bay was reduced, but full speed tow-nettings were taken covering a large part of the unworked area; and a series of full speed tow-nettings were taken to a position 50° 23’ N. x 1° 57’ W. (roughly eleven miles S. of St. Albans Head). At each of the stations, surface tow-nettings of five minutes’ duration were taken with the fine and medium nets. The nets used were of the ordinary open type, constructed of Swiss bolting silk of two sizes of mesh, the fine (A) embodying 70 holes per 1 c.m., and the medium (C) 18 holes per 1 c.m., the average length of a hole being .056 c.m., and the average breadth .036 c.m. At several positions oblique hauls, from bottom to surface, were made, but as the analyses of these samples were not found to differ materially in composition to those taken at the surface, they have not been included in the tables. The contents of the net were filtered through a net- bag of fine silk and preserved immediately in 5 per cent. formalin. In the determination of the samples, a general examination was first made under low magnification, the phytoplankton being subsequently submitted to critical treatment, under cover ship, with higher powers, 1.e., x 600 to x 800. In view of the fact that many of the developmental forms of metazoa, and certain of the more minute crustaceans occur more frequently - in the fine net, it has been deemed advisable to combine the analyses of both nets under a single column for each station. The comparative signs are those adopted in the International Plankton Investigations. But as it is impossible, by the examination of these symbols, to gain any exact idea of the actual bulk of a sample, the quantity of plankton taken was measured, after five minutes sedimentation, in a c.cm. glass, and the results are shown in the next table (Table No. 2). OF THE CORNISH PILCHARD FISHERY. —~y TasLe No. II. TaBLE SHOWING VOLUME OF PLANKTON COLLECTED BY EacH Haut. Ist Cruise. 2nd Cruise. Quantities. Duration of haul.| | Quantities. Duration of haul. | : | IF, Ss | F.S. 185 Sp JES | Station No. \A Net. C Net.| Net. |A Net.|C Net. Net. ||A Net./C Net.) Net. |A Net./C Net. Net. | |C.Cm. C.Cm. € Cm. Mins. | Mins. Mins. €. Cm. €-Em.|C.Cm. Min. | Mins | Mins. Mevagissey 1| 40 35 Ses 80| 3-5 Wetsreliser| 2| 30] 30 Sper benais lesa sll 3| 60) 20 sie kaae | SG\) BS heer 4} 45| 15 ligase Vagtety | 5} 80) 20 59 AD | 12:5 | 12-0] 6 |13:5| 35 bs x | | 7|105) 25 Sonia | 40| 25 es ti 8| 60} 70 Phe a es | | 9| 55] 45 ee lis | 60) 2-0 ie 10 80) 50 : seed| 11 |) 4:51) 1-0 ; & 10-5| 10 : » | 12} 90] 05 ate lince Lizard toFowey . 1] | enet | 12 5| | 40 | ee 2 | i 1125 40 Mounts Bay St. 10 to Lizard : | 6:5 40. | Mounts Bay : 1 | 5:0] 4:0 Se alan | | | G) HS) 1@ opel 50} 60 , . | 3| 50] 1:5 Cope: 1160] 7:5 s e 4/115 14:5 SST he I | 5 | 80/345 Aaiealle Sag || 27-5 | 16-0 Meal oe | 6| 95| 75 ee net | WEN OS are ded | | 8) 7:0! 4:5 ¥ fs ] 9) 7:5) 85 aeolian 10 }105| 9:5 “ Ah 1 7/3 GO 5 11 | 15-0 | 12°5 Ap | | Mounts Bay to Scilly 1} | 22°5 | | 70 uv Be ey | \ 23 0 70 Scilly 1 | | 18:5 | 31-5 He es 2 | | i} _ 24:0 1 a | 3 | | || 26-0 | 26-5 ne lh oe | S. Ives Bay 1 13y5)/ 350 ; wo ) OS) 0:6) Neseesnal (sea | 2| 85| 35 co TOBIN Tes ce teat te 3] 6:5)| 310 , ; 15| 45 ee Seen 4| 85} 2-75 ae 0-5} 3:5 lesen ise 5 /10-0| 40 ct ee 15| 025 . | 7 | ; 6 | 15:5! 30 5 a 05! 05 | 4 i Polperro to S. Albans ] l i) | | Head 1 | 105 30 2 | | 1:5 | k 3 | /140 a | 4 | | | 16-5, Pid 5 | | | | 175 | 6 | | ees 7 | | | 1/105 | 8 THE SCIENTIFIC AND ECONOMIC ASPECTS The writers do not desire to throw particular emphasis upon the value of this method of showing the extent of the product of each net for several reasons, the chief being the highly collapsible nature of certain organisms, notably Phacocysiis, when submitted to the action of a preservative, especially when it is stated that these determinations were made some weeks after the samples had been preserved. Yet, with this method of treatment in view, the tow-nettings in every instance were accurately timed, and the samples are | therefore to a certain extent comparable. When, as may be seen from the plankton tables, a general similarity in character exists between a series of samples, the simple process of add- ing together the figures for each net gives some indication of the sporadic distribution of the plankton generally, and a comparison of the two, taken in conjunction with a critical examination of the analyses, may enable the reader to gain some impression of the preponderance of phyto- over zoo- plankton, or vice versa.’ Further, it may be stated that, in order to render the results of the analyses as nearly comparable as possible, the survey of each area was carried out in daylight. The surface temperatures were obtained with a Centigrade thermometer by Negretti and Zambra (Kew Tested) for hydro- graphical work; the water samples were collected in bottles fitted with rubber corks (40z. capacity), and were tritrated at the Plymouth Marine Laboratory by Mr. C. W. Frost within one month of delivery. The soundings were partly taken with a Lucas sounding machine, whilst others (7.e., those marked in fathoms) are from the Admiralty Charts. 1 The authors desire to emphasize their full appreciation of the general recommendations with regard to plankton work contained in Appendix iv. of the 1st Rep. of the Advisory Committee on Fishery Research, but more especially that clause regarding the estimation of plankton. The wording of this section is as follows:—‘‘It is desirable that a special investigation should be at once set up by the Board (of Agriculture and Fisheries) in order to elaborate if possible a chemical or physical method for more rapidly estimating plankton or the organic matter of plankton in a given sample of water. Such a method, if evolved, would be of great value and would save much time, etc.” OF THE CORNISH PILCHARD FISHERY. 9 Tue PLanktTon oF MevacIssey AND St. AUSTELL’s Bays. An examination of the plankton tables (Tables Nos. 3 and 4), so far as they relate to the Mevagissey area, does not show that any remarkable changes had taken place in the composi- tion of the plankton during the period intervening between the two cruises. It is important to note, however, that the diatom flora has become. materially reduced in variety, as might be expected, by the end of August. In June the bulk of the phytoplankton was composed of the diatoms /izosolenia alata and R. semispina, together with Ceratium fusus. In August both of these diatoms had become comparatively scarce, their place being taken by the allied species R. Stolterfothi. But it 1s worthy of note that this latter species occurred in very sporadic abundance, rising from “rare” to “very common,” a fact which is further demonstrated by the volumetric measurements. From the tables, however, it will be seen that the sporadic distribution of individual species of phytoplankton is not so generally marked as it is in the case of the zooplankton. Thus in the June cruise, it is not difficult to trace the occurrence of surface shoals of Acartia Clausi and Temora longicornis, together with others of greater frequency composed of Zoeas, which in the present series were observed chiefly in the Megalopa stage. The samples taken on the first cruise, more- over, gave some indication of the interest which was forth- coming throughout nearly all the series, from the presence of a large and interesting variety of Peridiniales. Thus at Stations 1, 5 and 12 examples of Ceratium candelabrum were observed; at Stations 1, 3 and 9 C. horridum, and at several positions C. hexacanthum. Considered, however, from the food standpoint, the plankton did not appear to offer much attraction to drift fish. Reference to the volumetric measurements (Table No. 2) shows that throughout the entire area the product of the fine net was almost invariably greater than that of the medium, on both cruises; and in the light of our examinations it would appear that this disparity was attributable to a heavy preponderance of phyto- over zooplankton. By adding the products of both nets throughout the entire area we get 118.5 cc. of material B IO THE SCIENTIFIC AND ECONOMIC ASPECTS 47! 46! 45! 44! 43! 42" 44" 40/00 = WV 27/00 N 20" 78" 79! 174 16" MEVAGISSEY and ST. AUSTELLS BAYS. Roman Numerals = Station Nos. Open Circlés = Positions. Arabic Numerals = Depth in Metres. 15" OF THE CORNISH PILCHARD FISHERY. Wa collected at 12 stations on the June cruise, and 70.0 cc. for six Stations on the August cruise. Reducing these figures to common factors we find that the ratio is .84 for the July cruise to one for the August, a fact which may possibly indicate some increase in the general amount of plankton. Tue PLANKTON oF Mounts Bay. As may be seen from the plankton tables, a somewhat marked contrast appears to exist in the conditions of this area, not only in relation to those of Mevagissey Bay in June, but also between the results shown for the two cruises. It will be noticed that there is a marked diminution in the variety of the protophyta generally in June to that occurring at Mevagissey. The bulk of the phytoplankton, however, is still composed of the two diatoms previously mentioned, both of which on certain positions are reduced to rare and very rare. There is certainly a general marked increase in the amount of zooplankton, and this is largely due to an abundance of Naupli, together with Evadne nordmanni and Podon inter- medius, all of which were chiefly the product of the fine net. The generally higher markings against certain Copepods, e.g., Acartia Clausi, Centropages typicus, and Oithona similis are additional evidence of this fact. The most interesting feature, perhaps, in connection with the samples taken on the June cruise was the abundant occurrence of the copepod Anomalocera Patterson, at Stations 4, 5 and 6. We have already, in a letter to the Editor of “ Nature,” described in general terms the visitation of this species to the area under consideration, but an examination of the plankton tables will show the restricted extent of the shoal, an idea of the density of which may be gained from the tables of volumetric measurement. It is to be regretted that the weather conditions were unfavourable for any exact visual observa- tion, similar to that described by Mr. Matthias Dunn later in the year,® of the colour and appearance of the sea, in the tract of water supporting the shoal. 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pus ‘ds se;tpomuty Ayaiys pepsooas sv avasey ysig + ‘Keg seats keg s} UOT 6 SASL EnV ts) 3 (2881S edolesayy ,, ul AYaiyo papsooaa se eva0oZ 4 a gets Aessi sean 2) suoisuadsns ul Avg euryd y z = *“SHUVWAYY = ‘aug ana[ “aNZ ANA “Is, anal “ISTE AVIN ‘] (ON S31dV, 44s SNOILVLS TIy JO SNOILISOG Hog “€161 ‘au€ aNnf{—usrf avy ‘asIauD LSYIqJ— JT] ‘ON ATAaV], OF THE CORNISH PILCHARD FISHERY. | | TAja aa a)1a)1a) —] 41 +)4lofolal|tiat-f—|al|a}ala}al+|+i4 a faa)—fra “@BAIR[ puke PAO YSIY ‘G9 | SIISL|—DIDAIZAI A Oo )a}1] 1/4] 2 a1 |o9/0 jaa) a |1a]—]1alo |9990990}9}9}+)/9 99/1/44] © é : : : ; 2 PENIS 18) 4alta]—|—| =| =[bo tle) el +l a | ey =fealza} —|-—|=|-}-]-1-]=-]-]-]-] 9 “qalfiid ‘surpeareyur uopod’ ¢9 +} a}a a |ra|—]+| dlololoolol/o of4+]a}aja)a}—|a laajsajza —|+)+74] " ; : mdnen 29 ===] =l=|he 9D ]99/-+]9}9 joojoof—F—| 1 j1ap a | —jtajraji4 = tale at) — I — i : a ~ “ugaoy ‘tuuRtpiou suUpeAy “19 56) | 501] 59 \)pe|l sei} —t ||] XT] —j2}—|=jajapapa]—jrapa ya |) —jtay— | jay pra 2 ° z ‘ $ - avail ‘etpadraiig 09 ==|S)Sle}S||- =|=|=)=|=|=|23]—|=| |= | -|=|=|ea}zaj— 2a} 2 4+ : ; ; |BAIL[ ‘BEPIPVID 6G == \of ss] l= SS SSS SSS Sle Sa) 2 2S S ae Sra g : ‘sIeS O'S ‘SIIsB snyerqouy gg “P49499 VIIVISNAD Itt) —|—|—|—f1 | I)—J—}a)}a J+) —[2 apa) —] —] — | —]t4) a jaa} a frajo j aga 13/[0IN “AO ‘SIUIODISUOT BIOWBT “LG |) i]t | Be NM a oe tall | bea) Pea] ay pst et Sl ag | lf gay eet aie yIe0q snjyesuoja snuejeoopnasgd “9G +)+]+] 4 |1a)/-Jo a|—(aa} a} a) —) —feap—jaalra] —} = jaa) —] —| —| —]4a)-]- ‘sue(9 ‘snaied snuvjeorieg gg ===] \— —}aa}—|a1]—Jaa)2]-]-|-|-|-|-|]-]-]-|-|-|-|-]- yoaog, ‘SUBIN] VIPLOTAL “PS +) se} ] at |} yo ai+ti+lojojo|++]a1] 4] a jraizajsa] a jarajra) —jrajtajay ~ ° ; 3 ‘Sne[D ‘SI[IWIs EUOUJIQ “EG Tajrajrala|a|rajo lt] a |e] 4+ 4peaf—] -—] -—]—]-]—] 4} —] 2 jaalaazai4y : * asahoryy snoidd} sadedomusy “%¢ +] 41] 4)1] 21 }rafo +i+}a}a)a f+)+prafa | a }+)a fa} a |+]—jrajaa) a [zap “uu ‘snoIgoreuug snue[ey 1¢ (ft SE | | Sle) (forall ey St ll SY Sy SS Sih a bat ‘dulay (uosia\jeq eiaoojewiouy 0¢ Yee) || 99/9 ]9 19 Jool-+ +) ]+]+}/+'+!919 |9 00; +/090/9 |o J+ ‘ : ; ‘Iqsaly ‘IsN¥[D BNAVIW bP ‘ppogagog —vaanjsnag, Talaa) a} a |—|—f |e] +) +lzalzal ap] fraps [apa apa] apr faajrajaa) +) af : ‘oq ‘eororp einajdoyxtQ “gr ra) =lra] —|=}—]-] -|]—]=—]=|=]=]—]-—]-) -}-}-|aalaa —| -—| = Jaa] —| -—| —J2a}zaqa WIE pur Kon} ‘eyeyoundiq e}]1de8S “Lp —|=|=|=|=—|—fralaajaalaara)—jaa}1)a}a ~|—feal=| =| =|] —lea}=]=[ =] 2 apse aeaiel ‘eprjauuy “OF —|=|=}—Jral—JHi4l+)+)t+}a}ajajo}o;ogapey+|+ +4] 4]+)2aja]—| 2 taps ‘snayn(dourqoq “Sp =|=)=—| —)=|=f=)=)=)=)=|=) =} =) =| =] ye fa fran — ) =| =) = |=] =) =] FY auMOIg “LA ‘eidtu eiyaqQ ‘FF =|yalzalxa]—|—]—|aa]—| =|xalaal—|—]=]-) -]-]-|2a] —!salralaa]—|-]-|-|+]2]- ‘seg ‘canjejoundo}90 uintjasieyy «EF =)=)=}-)=|=f-)-J=}-}-) =}-1=}-) =] =f fal a =] = J =] =) =) =H weyqsutuuNng ‘eonjueyje vaeissny ‘Sh Xa}q 3/1 4a)13/13/1a) — 1a) —| —| —] —} —| — Jr ajaajr apa +]4 +4 l4}al}+}4}tlajojof+ sqyq enuedures sisdouunury, “LF | H ‘MiAva vOZMIa TT 19 00Z0{04g ~|—]=)=}=}-|-}-}-|=]=)-}=]-!-|=|=|=!-!l-I-] P : [9Jtayos ‘esoqoy3s sysAooaeyg “OF -|=|-|-|=]-|=]=]=|=|=/2a}za}-|-]=|=[2a]—|2af-] ; +" uiulayy ‘TaaatD BIOsIyoo1y, ~6E +Jaajaa} a |]+)+}a fag} a |to +) +y +i 4+\+)4jaaja jay : é “Z\IMUYDS ‘siprita erseydsojeyZ ‘SE ( ‘nAagaa vp6ygopory 4a}—|—|—|—|1a)-—]+] 2 |2a]— | —|—j24) —| —|aaj—|aa]—]a 2 : ‘Sqyq ‘SUBOIMI UINUaI0I0I1g “LE =|=)=|=|=|—)=Jraf=|aalanzalra}aa} a |—} a jrajra) a f+] - : : i “Bro ‘I1uta}S oo ‘98 +)1]41 =|xalxa}—]+]4+]+]4|—|za]—| 4 |aaja + |4141)—]4 “ JIsO ‘umpryyped us “G¢ —|-)-|}-]-]-|}-fa]-|]-/-}-!]=|]-}=]-|-!-|]-/-]- ‘ureyS ‘sntnqoys us “FE +] a] ad frat ajay af ]a] a ira) rt) a) tj} a]—j) a jrtaaaypa ? 2 [leq ‘umsseidap ig “$e 1a{tajra) —j1a)—| —[+9+)+) 1) 1) 2) 4) tra) a }4+frajrzapa 3 : ‘URIDD ‘UINOTUOD WINSUIpIIag 'ZE —|ra}—|—|—|—] —J—J2a)— jaa) -|-|-|-]-]—-]23)-j2apeay 8 g ‘squy ‘ejnoe oo ‘TS =| —]—} =Jaa)—] —Joafe a) — | —j24a)—]aa}—|-}—-|]-|-|-]-] ‘yoey pue ‘des ‘eyepunjorsisAydourq ‘0g I jaa/ra| —)| — la ajraf+] a |rajzaj—|—j2a —|-}—}—|21)-]-] ~ ; i “ysieg ‘eynoyuel siyjesdojdiq 62 “paInuiquoI—"TTT “ON ATIAVT. THE SCIENTIFIC AND ECONOMIC ASPECTS 14 | =| == =| Rabralgiea = —fra) [+)+) +} 44/127 4)13)13]+ alls aj}12 alas =|—] * : g ‘SqyA ‘SUBOIU UINA}UBDOIOIG “EZ —|-|-'-|-|-|-]-]- al=|= =|[- x | —|safraaalra'sa} a |—]+)+)4]4 aaaajza}—faal ‘ : * -3ysQ ‘winpryed rt ‘8G -|—|—'-]-|-]-J-]-!-!-)=]|-]- azafrajzaj— —|xa'13|-|-]-|-]-]-|-|-|-|-|- o 9 “FSO ‘suas1aAIp “ IG Td) qa jaa X jta)4+) 2 faajaa —|—jraqtapzs +)a)+]2) 2 T/T)+)r1fo;/9lOf4+)/41) 4) 1 \ta4 o = 2 “Teg ‘wnssardap Ms 0B === =F 1S Fe SENSI = =f) —]= sajeaaajzay)—fa | ajay—|—)—|—|—|-7 ; : * "URI ‘UINOIUOD UNIUIPIieq ‘6T O}o}a)1|+)o0) of1ajta114113/11)+ Oyo }+i4+ +/+, +)9 ]4]9 |99)97+)+ 4) 2 jrays g “ysiag ‘ejnonjuay stpesdoydiq ST —|—|—'-|-|-|-]-|-|-|-|-|- Zaft ajay) |=) =| =|] ) tat |) |=) | — : gs + “janition ‘sodin LT SVS N= SNES Xaf—jraj— — | 1 \aajra)—}a)} 1) 1tq—)—-)| —\241)-]- "yory pue deg ‘eyepunjo1 a “OT =) =|=—|—|—|za1afra)—|—|—-—]-)-]- S/S) 35 =| —|214/ 4 2) —J+)+|+}2ajaa) — 24) —]24 “2 yyq ‘eynoe stshydourq “ST t}alaa a }+lo‘ooj+}+!+]+)+]+]9 a fpoloof 9} +)90]9}9|+]9j9090}9)+)/+/+4+)4]+ JIN, AO ‘sodrs} ue FL aa} Par lsalra}a |x faa|—|=|=|=|-]-| |+]-)2]2 2a}44+\+)2]2]2}2,o/4)4+)+)2]+ . jreg ‘sodiSuoy =‘! eT —|/—|—) —|—] =I} =] =| — | =| = 1+ aayf—|afa}ajol/+|+}+}o}o)9}9)/+)/+/+)-]4 * yorinoyy ‘UInyjUPOexeY of CI +\4)a)a}+)ol+t+)+)+j)4+}4+)+]oo) |o 72 jooj+] a [+)+) 9) 2] 9 jooof--| a | a jra)—| — : . - sqyq ‘snsny si “yey fpf eh lh ttt dp a eed CY EY RR) fh tf te) Us a Fa a ‘ * -yoey pue dela ‘eoinj wnneiad ‘OT \ *Sa)VINIPIAIg —|—|—|=|—jaa| 1 frajzaraagj13)+}— —[ra)ral+) 1} 9 Joo|o0|13Jo0)+] 9Jo9) 9)+)09)1] 07 ° : * -Se1ag ‘1G}Of19}10}S 4 6 =} =) =) ) = lara) ef lr a'ra) = lralaapra) jaa —|rapar =] a |) a )—pa say poy+i+i Fiza ; * “gAa[D ‘lejosqniysS at 8 =—|=)—|—|=laa/af—]—|=—!=|=Jaafoa) [aaf=| —fra) | fa jt izapr|+]opo}+)4+)+)r3aj+ : ‘suazy ‘eurdstwas is L Salts — |X 14j14}—|14)—|14) 1 jtt —|-|-pP4 2 $y t+)+jray+) z)4 y+) 4] 2) 2 jraa G 3 ‘MyIg ‘eye[e VIUs[OSOZITYY “9 —|—|—}—|-—|—|—faajasa}a|—|a}+]- ==) =f) = |r x a3]23)—]— |2a)—fr ayaa) —| —|—}— ‘seiog ‘epiooey eipivuins) °C —|—|—|—|—|—|—[aalaa13)—jartajra) jad tajtajrxtajra)— Pipe dig) Jy yp ho “3qqq ‘SN}eIpeI SNOSIPOULNSOD =F —|—|—|—|—|ra}af—|—|-)-|-|-]- —|—|—praaajca) 2) 1 jraf+)+) 4+] 0)+\+)+\24)+ dA9[D ‘UInsusp ue g —|—]=!—)—Jra'za]—|—]=-|-|-|-]- —}—|—prasajza 2] a jae Sl eae 2) eae | ele ul ; : ‘ "Treg ‘a[ea1oq seilsovjoeyD SG —|-|-|-|-|-|-]-|-]-|-|-|-I- —}-|-J-)=-)=-)-}=)-]-}-)-]-)- 24 -]- 24) : 3 * ‘jauy ‘exopeied erseypioeg = “T | -ap29vMmojn1CT Pallas) 9\G PIE|S| FLE\2\F 0F 9|S €\¢ HF, 6\L)G/8)F “SON UOl}R}S HIELE + * \ a Lt) = | ae in| [4] Jen ip>|{he>| tes} fheo| es) Leo ile} wn} P : Ww | | W) W) W) w) s Z Nn S g Ss ‘114saspiuisap ¢ vyjindg ~all eal orl esl ea bos “ATPIOS 5 g z S \< 5 skeg $112} jO avaayy Aijairyo paqiosap sv ,, VAIL] aepipEaLD ,, t ‘punos Ren euler 4S pue jUOSILECLUOSS ‘Keg saat 3S Ss (Are a\s S ve 3g aaa yo sasodand soz azeordnp us uayvy seal 3S [ “ON + = a 4S w a on s = : W *paansveul 40 poultusajap jou 2ajdures 4ysang 3aN V % : Ble c i} *SHUVWAYY Peay sueq{y 3S ai S mi s 0} o11adjog FO “| EH eq squnoy |8|-/< i ei aS ‘T ‘ON a[qe 90s suor}e}S ][e Jo suontsod 104 *€161 ‘HLQZ-HLOZ ISNOAY ‘ASINUD GNZ—"AT ‘ON AAV], 15 OF THE CORNISH PILCHARD FISHERY = ADT A) — | —f tr [1 4s. afr ajyzafaa) 1) 1) 1) —] 41 CQ) = jt Apt Aji a) — }1 4) 1a) 1 3, : : : = ¥ oeAIeT pue PAG) “6S ‘SIISIT I A /4t4) =) =f 4 | taf a) a fra) a jrasrajra) a prajia) —frajta) —| 1} a} a Mi : , rf i s 9e907 8s = ajra)—|—fat) ar) —pa)apa)+) a) a) at joap—lra)—f—laa)/—}—]—Jaaf «: : e * -qaliry ‘sntpeuajur uopog ‘z¢ ar Ata) — |) Ft raza | i+} oO) +} +) +}+2} 1)/+folo}/+tlololo : g F BONO! geo ZON| aupeaAq ‘9G 99 9/9) 9} 9f99/99/59F9}+79)9)/+)/+/9}/+f9]o)/+$4+)+)+}+)+)+ : : : z : ‘ jdney ‘ce 34 A) = 1a) —F 4 fraitafrafsapa | a) a) a) al apa) alapas+i+i4+iaal-] - ; : f aeaiyy ‘erpedtitg “pg = +} =} =) 9+] 2) a P=} —fral a | — J afro} af — | —] —Jralaal —Jaa) alsa Z : © 3 " 9PAIL[ ‘SepIpeEIeD EC ‘Aa439 VIIVISHAD 2) T/1a) 1 )+999)9] fo} 9fo90/90] 9] a /oo}o J++) +] a +) +] + +}o}+ : : ‘IOIQIA AO ‘stuIOOTSUOT eIOWST, ‘ZS o) H ital TYP) rt icap |e ey] |p 2] —Jrap—Jral—faairal—-] : " yonog ‘snjesuoja snuvyeoopnasy ‘TG 99 +) —}4/+f 4) 4) afoojofo}o}o}o/+/of7+/+/4}a)+)/+/+)/4+]+ : : : : ‘sne[D ‘snaaed snuveorieg 0s = =|) S)S[ralratrol| sap —jaralr a —|—| fra] =| —f—}—|=}=}=]=] ° : 9 pireg ‘essjruinyd " '6F 9 AatA API |+)9foo/9f9)o/+/+)o}/ofo}o}of+/+}+/+)a}a] - ; g 2 ‘SNY[D ‘SIIWIs eUOYIIG “EF es =o aaa islstl liai| SS) hdl Sl Sl Slee PSHE © : : Apeag ‘Voljuepe e[[a}eso1, “ZF pS ==) ==) —) f=) —f =] =) =) laa] — | = | af —Jr a —]—]=]-] - 6 Q : “yoo0g ‘Suan PIPlajoW OF = 4a}—|=|—]—|=|—fra} apa s+)a}+]+]+fpo]o}+folojojol+i4y - "7 Bue ‘suosyynoe ediajny “gy + —}—|-[24)-|-]-|-fa}+)4}2}/4+)afa)} 4 foafa] a) a4] afaala 4 qquy ‘snorsue snaeohi0g ‘FF @) +|+] 9. [99/99]99foajoof99 9 Jo Jo ]9 Jo f+]+)+1+]+]+]o0} 9 4 ‘ saho1y ‘snordd} sasedomued ‘gp co) TPF) F Pie P44] a yA] a foafea] a faa} a frat: i 5 WEIND) ‘snorpolemuy snurleg Zp = + }44) — [44] dt farapr fraps) — Jara} a | 1 }raf— fra] —f—Jra}—|-}-]-] - ; ‘daar ‘Y ‘Tuosie}jeq Bisoojewouy [FPF I TATA) APTA | APO] ++ j+i[+i+]o9}+}o;ojajojojoy - : g ‘AQSOIDH ‘ISNR[D Bey «(OF ‘wpogagoj—vaansnad I =|=|)=f-] Jaafar} apa} a) a frajza} a q+)4)afaala}a}a salad: : : : ‘104 ‘BolOIp wana[doxiO 6e 1 —|-|-}-|]-}]-}-}-]-/-|-|-Jaa})—]-/aa] —[a Jaalaa}aal—Jaal - ; y * “Wap ‘esIaaoijal ‘euloeully ge + FYE) IAP] P4444] 4) +p a [4+ faapeajaaira} a |+ rap - : wes pue Song eye;oundIq eWISeS LE Id =| =} —f2a) =} — fal fralra] — | —} — frat — Jaafar af—frajaa}—|-|-] - é SEALE] ‘epljauuy ‘ge ai SNS Sty fess fee ee Ss ery ise aed fsa Hes alsas] bist oe fae lf seh 8a (seal | : : G * 9eAIe] ‘eyeUapoulyoy ce = =| =f P—] —| — fe afzafr air aja afra) — jrap—| —|—]-jarajaalra}—|-] : : : “SIV JA ‘esajtjoid eisieg “PE - =|-|-}-]-!-9f-/-9}-}-/-]-]-]-9-]-|]-]-|-|-Jaalaal-] - SUR Ox et ‘La ‘wnaprojequiAo winipreryg ‘ge = = 4a) —F—] =| —f a] + fra) +)+] —] a | a frajzalazafica) a faalzal—|-] - : SuMOre ‘L'a ‘eistu eljaqQ ‘ze ~ Xa/ta}—}—|—|—f—|—J—jaa)—|—| —| a fra}aa) —frajzalra) —lzalaa] : * sires ‘uinjzejoundoj90 uni [asiey TE ~ =|=|-{-]=|=f-|-[xa}—lealaa} 2 }-]-)-]-]-|aa}-]-|-|-] - : : : seqio. ‘ejeine esfydnq ‘og = 11 — |=) =] -|44] -F =] — fra] —] —]-ltal-7-]-]-]-}]-}-]-]-|-] - : ‘ ' “poy ‘snaid viqoeiqoins,q ‘6% - =}—]-P4)—|—-pa} aga |4l+) 2 fra}+fca}4 foafaa) a} a] faasaa] - ; 9 ‘ Asien) ‘eOlJUR[}e BavIssn| ‘gz —|aa = {=} =]-)24) -J=) =F -]-] =| -Jazal—f Jaap a4 }a}af} ata local: ‘ ; [O4 ‘ByepnoNUap stjAo01"}}49 “Lz - —|=|-}-}-}-}=)-]-}-|-)-)=-|-]-J2alsapa Jaalsajaa}a fraps - : ' -sqqq ‘einaedureo stsdouunury ‘97 ‘DIAVA VOZYII 44 00204017 qa\11 4a) —)tay—} =) —J—| —]—] = jaa} —| —} —Jra) — Jaa —| - Jaa} —]-]-] - : s : “UIST ‘TaAa[D BIOsIyoOIy “Cz -|- TAA Taprsa; |x px | ar y—] ax fraizajra}—fa|+)+) a jaaj—jra)—jaal : B ‘Z\IWIYIS ‘srplita esraeydsojeyy FG “aaa £41 G0J0AT “panutjuoI— AJ] ‘ON ATHY], THE SCIENTIFIC AND ECONOMIC ASPECTS 16 ~(q) swoure *(W) setteap; ul yideq = spesownpy siqeay *SUOIIISOY = S2]D1ID UedcG SOK] UONYIS = S[eJowWNA] UEWOY ‘AVG SLNNOW OF THE CORNISH PILCHARD FISHERY. 17 hardly think that this copepod plays any important part in the diet of the pilchard in English waters, but we take into consideration the statement of the late Mr. Matthias Dunn‘ to the effect that he had observed the stomachs of fish, pveswmably arriving from deep water, containing large numbers of Anomalocera. The following remarks upon the occurrence of the species by Prof. G. O. Sars,*® moreover, would seem to indicate that an occasional abundant occurrence of the species in inshore waters would afford ideal food conditions for drift fishes. This author states :—‘I have met with this form in several places, both off the south and west coasts of Norway, generally con- gregated in great shoals. The true habitat of this form, how- ever, 1s undoubtedly the open ocean, and it is only after heavy gales, and by the accompanying strong sea currents, that it is occasionally brought close to the shores and into the fjords. . . . Off the west coast of Norway, where it is known to the fishermen as ‘ Blaaaate” (blue bait), its presence in the fjords is a very good sign of the approach of the summer herring.” So far as the area under consideration is concerned, we can find no previous record of an inshore visitation of the species in large numbers, and an examination of the plankton tables published in the International Bulletins shows that the species has hitherto been generally recorded in comparative frequency only at the extreme western stations (Nos. E4, Es). It is perhaps worthy of record that a fair number of young fish were taken with the coarse tow-net on the same positions at which Azxomalocera was very abundant, and these upon examination proved to be J/o¢ella sp. ranging in length from 7 m.m. to 19.5 m.m., damodytes sp. from 8.5 m.m. to 1g m.m., and Clupea ? harengus 18 m.m. (one only). We dissected out the stomach contents of several of the rocklings, and found that they consisted chiefly of Acartia Clausi, Calanus finmarchicus, Centropages typicus, Naupli, etc., im many cases in an intact condition, but in no instance were we enabled to detect the remains of Axomalocera. 4 Dunn, M., ‘“‘ Migrations and Habits of the Pilchards,’’ Lectures on Fishes, etc., County Fisheries Exhibition, Truro, 1893, p. 159, etc. ~5 Sars, G. O., ‘‘An account of the Crustacea of Norway,” Vol. iv. ““Copepoda,’”’ p. 140. ? 18 THE SCIENTIFIC AND ECONOMIC ASPECTS Passing now to a consideration of the plankton taken on the August cruise, we observe a similar change in the diatom flora to that already noted in the case of the Mevagissey area, namely, the general decadence of the two species, Rhizosolenia alata and R. semispina, and an increase in the growth of Rhizosolenia Stolterfothi. The condition of this last named speciés, moreover, is somewhat remarkable, occurring as it did in very sporadic abundance. Thus, at Stations 3 and 5, and in the full speed netting between Stations 1 and 5, it was met with in such profusion that the nets became choked after a short immersion in the water, the product appearing as a dense glairy mass, whilst at Stations 2 and 6 the species occurred in an almost negligible quantity, and at the outer Station (No. 10) there was a considerable diminution. In the samples taken to the west of Mounts Bay and in St. Mary’s Sound, Scilly, the species was practically non-existent. With regard to the Peridiniales, an examination of the tables shows a general increase in certain species, notably Ceratium fusus, hexacanthum, and tripos, Diplopsalis lenticula, etc., though it will be noticed that the heavier gatherings of C. fusus and tripos were taken by the full speed net to the east and west of Mounts Bay, and at the Scillies. With Ceratium hexacanthum and longipes, reference to the tables will show that their distribution was not so marked in the extreme western area as it was in Mevagissey Bay and the adjacent waters. The comparatively close inshore occurrence of Dinophysis t1pos between the Lizard and Fowey, west of Mounts Bay, and at the Scillies, is also a matter deserving of comment. In the case of the zooplankton generally, the tables of volumetric measurement show more clearly than do the plank- ton tables the contrast existing between the samples taken in Mounts Bay and those from the Scillies. In both areas it will be seen that the predominant species are the Copepods Centropages ty picus, Oithona similis and Temora longicornis, but that in St. Mary’s Sound, Scilly, the samples were of a much richer character ; an important feature when the contem- porary condition of the fishery is considered. OF THE CORNISH PILCHARD FISHERY. 19 ST.- IVES BAY. Roman Numerals = Station Nos. Open Circles = Positions. Arabic Numerals = Depth in Metres. THe PLANKTON oF ST. Ives Bay. But few features of interest appear to exist between the composition of the plankton observed at the several stations in St. Ives Bay on both cruises, but generally speaking the contrast between the samples taken on the first cruise and those of the second is somewhat remarkable. In June, as it may be seen from the plankton tables, the whole of St. Ives Bay was literally choked with Phaeocystis globosa, to such an extent in fact that the contents of a bottle filled over the 20 THE SCIENTIFIC AND ECONOMIC ASPECTS ship’s side appeared to be composed entirely of the species, amongst which a few zoeas seemed to struggle for existence. We do not maintain that the analyses of the samples can give the reader a just appreciation of the actual composition of the plankton, in view of the fact that both the fine and coarse nets undoubtedly ceased to filter after a very short immersion. The chief point of interest which we have to consider, therefore, lies solely in the fact of the profusion of this flagellate in St. Ives Bay, whilst it appears to have been entirely absent from Mounts Bay. It is well known that Phaeocystis globosa is a neritic species, belonging to the so-called “periodic plankton,” and as its term of vegetation is comparatively short, it was a matter of no remark to find that, on our second visit to St. Ives Bay in August, it had entirely disappeared. Yet an examination of the volumetric measurements of the samples taken in August shows that the quantity of plankton generally existent in this area, after the passing of the Phacocystis, was very slight indeed. A dis- cussion upon the causes of this phenomenon: as to whether Phaeocystis crowds other forms of the plankton out of existence by its rapid propagation, or in its decay renders the water insupportable for a time to other organisms, etc., is beyond the province of this paper. Apart from Phaeocystis, the general composition of the rest of the plankton, so far as it was possible to judge under the deterrent influence to which we have already referred, 7.¢., the clogging of the nets, appeared in June to present several features in common with those observed in Mounts Bay. For example, the two diatoms, Ahizosolenia alata and R. semis- pina, again make their appearance in varying abundance at the several stations, and the two Copepods, Acartia Clausi and Oithona similis, are also fairly well represented. In the August cruise, however, the substitution of Ahizosolenia Stolterfothi for the two allied species already mentioned was not observed. The only point of some interest in connection with the zooplankton was the occurrence of Anomalocera Pattersoni at five of the stations. This copepod was repre- sented, however, solely by zwzadzlt individuals of the species. OF THE CORNISH PILCHARD FISHERY. Cll GENERAL CONSIDERATIONS UPON THE PLANKTON OF THE CornisH INSHORE WATERS. In considering the condition of the plankton observed as occurring throughout the several areas studied, together with certain other facts, we find that there is some evidence to show that an abnormal influence was at work during 1913. As to whether this condition had existed to any extent in 1912 it is impossible to determine ; but, if we associate possible cause with now well known effect, and attribute the extreme eastern migratory movement of pilchards in 1913 to such abnormal influence, we have also to take into consideration the state- ments of fishermen at Brighton to the effect that pilchards were taken there regularly, in small numbers, during 1912. Thus, if one might be permitted to speculate upon these facts, it would seem possible to suggest that in 1913 these conditions had become sufficiently pronounced to bring about an effect so marked as to engage attention. But we have now to consider in detail such evidence as we hold lending support to our theory so far as it affects the year 1913. Unfortunately the only previous observations which have a more or less direct bearing upon the area under consideration are those taken in connection with an investiga- tion upon the mackerel’ in 1906-7, together with others taken throughout a greater number of years upon the International Plankton Cruises at Station E.7," which, it is to be regretted, is situated at some distance outside Mounts Bay. With such slender evidence of the planktonic conditions existent in former years it is impossible to do very much in the way of comparison, but certain facts are too obviously of importance to be overlooked. We have already remarked upon the abundance and variety of the Peridiniales occurring in the plankton samples. With regard to Ceratium hexacanthum, we can find no observation of its abundant occurrence in the Channel, other than that of 6 Vide Bullen, G. E., ‘‘ Plankton Studies in relation to the Western Mackerel Fishery.”’ 7 Vide Plankton Tables, ‘‘ Bulletins de Conseil International pour l’Exploration de Ja Mer,’’ 22 THE SCIENTIFIC AND ECONOMIC ASPECTS Gough® in 1903, who recorded it for the south-western area alone and only in February and November. From the plankton tables it will be seen that this species occurred in comparative scarcity at Mevagissey in June, increasing some- what in abundance and extending its distribution to the Scillies in August. In view of the fact that the species appears to be an oceanic one, its greater abundance in the full speed nettings which were taken on the run of the ship’s course well out to sea, would suggest that it occurred in some profusion outside the close inshore waters of Mounts Bay and the adjacent area. It is important, moreover, to note the sporadic abundance of Diplopsalis lenticula in August, and the occurrence of Peridineum divergens, Dinophysis tnpos, Muicrosetella atlantica, Oithona plumifera, and Limacina ? retroversa, to understand that in the coastal waters we have observed certain forms which have generally hitherto been associated with the plankton of the extreme western area of the English Channel. In this connection, moreover, it may be mentioned that Gough’ states that Anxomalocera Pattersoni may be regarded as a species generally occurring in the Great West Bay. We thus have some evidence to show that the plankton of the areas under consideration was of an abnormal character, and in the nature of its composition lending support to a theory that extreme western biological conditions were existent further to the east than in certain former years. Certain other facts are before us, which might possibly lend some support to a still wider view of the matter than that which we have already indicated. We refer more particularly to the occasional visita- tions of shoals of Physalia, which extended to our personal knowledge as far east as Studland toward the end of May. SALINITIES OF WATER SAMPLES. The analyses of the water samples taken within the area under consideration, and the absence of similar observations derived from Mid Channel and elsewhere however lend no 8 Gough, L. H., ‘‘ Rep. of the Plankton of the English Channel in 1903,”’ p. 333 Int. Inv. Mar. Biolog. Ass. Rep. I. 9 Op. cit., p. 335. OF THE CORNISH PILCHARD FISHERY. 23 useful evidence in support of the above theory. For it will be seen, on reference to the salinity table (Table No. 1), that no remarkably high salinities occur at any position. On the May cruise the highest figures are 35.12 for the extreme southern and eastern stations (Stations Nos. 9, 10) in Mounts Bay, and 35.18 for two positions in St. Ives Bay. In Mevagissey and St. Austell’s Bays there is a drop to 33.31, rising to 33.74 in the three extreme eastern stations (Stations Nos. 1, 2, 12), a moderate constancy ranging from 34.6 to 34-7 obtaining farther to the west. On the second cruise in August the salinities recorded throughout the entire coastal area vary only in the second place of decimals, from 35.02 to 35.08. The samples taken in St. Ives Bay are very nearly similar iver se, but generally very slightly higher than those of Mounts Bay and the Mevagissey area. A contrast certainly does exist between these samples generally and those taken in St. Mary’s Sound, which show an increase to 35.2; a fact which, when it is remem- bered that the samples were taken in enclosed coastal waters. may possibly indicate the presence of water of higher salinity in the comparatively near vicinity. From the above observa- tions, it 1s obviously impossible to draw any definite conclu- sions; but, when considered in the light of what is already known regarding the physical conditions of the Channel,” some importance has necessarily to be given to such a material increase within a radius of 50’. THe PLANKTON OF THE EASTERN AREA. It is to be regretted that circumstances precluded a more thorough investigation of the planktonic conditions existent to the east of what hitherto has been regarded as the pilchard fishery area, and that the observations, such as they are, con- sisting solely of full speed tow-nettings, were not continued up to the Straits of Dover. For, lacking as they do the full value of samples taken by the ordinary tow-net at regular stations, the gatherings of plankton taken between Polperro 10 Vide Matthews, D. J., ‘‘ Rep. on the Physical of the English Channel in 1913,’’ and other subsequent papers. 24 THE SCIENTIFIC AND ECONOMIC ASPECTS and St. Albans Head afford many points of interest, and lend much valuable support to the general considerations upon food conditions. We have to consider the bathymetrical rise and fall of certain species, the long distance covered by each haul (about five miles), in which it was possible to run through one or more shoals of various organisms, together with several other important points, in making any comparison between these samples and others taken in the western area. But the examination of the analyses shows at least one very important point, namely, that phytoplankton gradually decreases to a minimum from west to east of the course covered, and that what we may justly regard as desirable food species increase in abundance. The seven hauls comprising the present series are comparable zzder se solely in length of duration (thirty minutes each), and for the reasons previously stated it is obviously impossible to draw any exact deductions. Yet from the evidence afforded by the volumetric measurements of samples Nos. 2 and 6 taken almost at the extreme western and eastern points, it would seem possible to suggest that throughout the area covered the distribution of the plankton generally was very sporadic. The appearance in comparative abundance of that most important food species, Calanus finmarchicus, in the eastern area, hitherto noted in comparative scarcity in the coastal waters of the west, is another matter of some importance. But, in comparing roughly the last five samples with the two full speed nettings taken from Scilly to Mounts Bay earlier in the cruise, we find that the actual volume of material is somewhat higher for the former ;" and in view of the fact that this plankton consisted almost entirely of animal matter, we have some evidence to show that the richer feeding grounds lay to the east of Plymouth. 11 Note.—Our method of comparison has consisted in adding together the total volume of (a) the five last samples of the eastern series and (b) the two western (Scilly-Mounts Bay), dividing each product by the total number of minutes occupied in the collection of each. The comparable figures gained im this way are 325 western, 383 eastern. When it is noticed that one sample of the latter series consisted only of 0.5 c.cm. of material it will be seen that the contrast is not without some significance. OF THE CORNISH PILCHARD FISHERY. 25 THE CONDITION OF THE PILCHARD FISHERY CONSIDERED IN RELATION TO THE PLANKTON. In a previous paper’ it has been shown that an intimate correlation appears to exist between the plankton environment of inshore waters and the extent of migration. It was naturally to be expected that the quantity and suitability of the food supply should constitute what, in the present state of our knowledge, certainly appears to be the predominant factor in a profitable fishery. For it has never been suggested that the pilchard moves into inshore waters for any other purpose than that of seeking suitable feeding grounds. Cunningham” has described the pilchard as being the most truly marine clupeoid frequenting the coastal waters of Great Britain; and it is a well-known fact that the species, unlike certain of its congeners, habitually spawns at some distance from land. That the family trait of seeking brackish, or even fresh water, occasionally manifests itself, however, is evidenced by the now well-established fact that pilchards may often be taken in the Fowey river as far inland as Lostwithiel.“ Yet upon occasional instances of this character we can adduce no useful evidence to show that the pilchard seeks the coastal waters from necessity. It is well known that the fish forming the subject of the Cornish fishery are for the greater part in either unripe or “shotten” condition (shirmers), and in this respect the pilchard may be compared with the small immature mackerel which move into coastal waters, after the advent of the spring shoals. In considering the migrations of pilchard, therefore, we are probably discussing movements which are undertaken for no other reason than that of feeding. Yet in making this statement we do not desire to be too definite, since in dealing with a species whose near allies seek fresh water for the important purpose of spawning—a species, moreover, which occasionally seeks similar habitat itself—it is impossible to say whether an atavistic tendency may not be in evidence. 13° Mera’ No: 1-27 13 Cunningham, J. P., ‘‘ Mark. Mar. Fishes.” 14 Teste Mr. Moses Dunn, of Fowey, and several other local observers. 26 THE SCIENTIFIC AND ECONOMIC ASPECTS On the coast of France, Portugal and elsewhere, where the sardine industry is prosecuted, the success of the fishery is well known to depend largely upon what may be termed the caprice of the fish in appearing at certain stations at more or less regular seasons. The uncertainty of this fishery alone appears to afford some evidence in support of a theory that inshore migration is determined largely by the attraction afforded by the coastal waters from the food standpoint. Yet, bearing in mind the normal delimitation of range of the species, we have also to place important consideration upon sea temperature and salinity. It is not hard to believe that if physical conditions approxi- mating to those existent in the normal habitat of the pilchard were to extend beyond their usual limits, and that the fish in migration found no suitable food supply awaiting them in their usual summer haunts, that migration might be extended farther afield within the area exhibiting suitability of habitat from the phenological aspect. We have already summarized the somewhat scanty direct evidence at our disposal, showing that certain planktonic conditions, usually associated with the extreme western area of the Channel, were existent in the coastal waters of Cornwall during the summer of 1913. The meteorological observations” for the south coast of England in the same season show air temperatures generally above the mean for July, August and September, and our own observations tend to show a general surface water temperature distinctly above the normal. The visitations of Physalia and certain other forms of Mediter- ranean fauna had also been noted. So much for the evidence supporting a theory of the extension of suitability of habitat. With regard to the unsuitability of the food supply existent in the coastal waters of Cornwall, we may refer briefly to the high proportion of phytoplankton over zooplankton in Mevagissey Bay, St. Austell’s Bay and Mounts Bay, the literally choked condition of St. Ives Bay in June, due to Phaceocystis, and the extreme poverty of the plankton remain- ing there in August. And when we compare these conditions 15 ¢de Appendices to the “‘ Daily Weather Reports ”’ of the Meteorological Office. OF THE CORNISH PILCHARD FISHERY. 2)7, with those existing farther to the east, and in the Scillies, we find that suitable food conditions certainly did not exist in the usual summer fishery area. Summarizing briefly the condition of the fishery, we find in the effect some remarkable evidence in support of the probable cause upon the lines which we have already indi- cated. It is now a well-known fact that the migratory move- ments of pilchards extended as far east as Deal. From information derived from fishermen at Brighton, it appeared that regular catches of some thousands had been made a few miles off the coast in the adjacent waters and up to the Straits of Dover, throughout the latter half of July, in August, and well into September. It may be mentioned that we examined the stomach contents of fish taken off Brighton in September, and found that they consisted largely of zoeas and certain Calanoid Copepods, notably Calanus jfinmarchicus, Centro- pages typicus, etc.—food of a character which we have often met with in fish from the western area in former years. During the months when pilchards, the catches of but a few drifters, were being marketed regularly at Brighton and elsewhere under the fictitious name of “herring,” and one firm at Deal" were accumulating as a ““ by-product ” over five hundred barrels of fish cured as “ bloaters,” the Mevagissey and Mounts Bay fishermen were securing slender catches of but a few hundreds per night. In the Scillies, however, where something in the nature of an experimental fishery was being carried on, chiefly by men who had little previous experience of drifting, the fish appeared to be present on the ground in sufficient quantity. It was not until the beginning of October,” that the Mounts Bay fishery became in any way productive; and it is a signifi- cant fact that this change was practically contemporaneous with an observed inshore visitation of a large shoal of the two Copepods Anxomalocera Pattersoni andCalanus finmarchicus. In an important paper on the mackerel, Dr. E. J. Allen” 16 Teste Mr. Matthias Dunn, of Newlyn. lt Vide ‘* Mera No. 1,” p. 20. 18 Vide ‘‘Mera No. 1,”’ zd. loc. 1) V7de Allen, E. J., ‘‘ Mackerel and Sunshine.”’ 28 THE SCIENTIFIC AND ECONOMIC ASPECTS has tentatively shown that some correlation may be found to exist between the productiveness of the fishery, and the extent of bright sunshine occurring in the early spring months, prior to the fishing season. This author states, ““ Experiments on the cultivation of marine plankton diatoms in the laboratory, upon which I had been engaged, had drawn my attention to the great importance to be attached to the intensity of light to which the diatoms were exposed. It therefore occurred to me that a special abundance of Copepods during the month of May might be due to a special amount of sunshine during the earlier months of the year, which would increase the amount of phytoplankton, the Copepod food. An attempt was there- fore made to correlate the average quantity of mackerel per boat taken in May with the number of hours of bright sunshine recorded during the first quarter of the year.” The observations upon which this paper is founded appear to leave little doubt in the mind of the reader that, under what we may term ideal conditions, such a correlation probably does invariably exist, but under the present inadequate system of fishing by the majority within a comparatively confined area, the official statistics of landings, as the author justly points out, lend but little support to such a theory. For as one of the present authors has already shown,” a superabundance of phytoplankton in coastal waters appears to correlate with a poor mackerel fishery, and to a large extent the findings in this and a previous paper (Mera No. r) indicate that the same may hold good in the case of the pilchard. It follows that we have to go beyond the limits of the area affected by the majority of the fishermen, in those years when phytoplankton is abundant in the coastal waters, to find evidence of the more exact working of this cycle of events. For as it now stands, a superabundance of phytoplankton in coastal waters, food of a character unsuitable to the fish themselves, appears to form a powerful factor in the delimitation of the extent of inshore migration. It follows that it is necessary that this vegetable plankton be consumed largely by the zooplankton before the fish are induced to approach in appreciable numbers to the *0 Bullen, G. E., ‘‘ Plankton Studies,” p. 281. OF THE CORNISH PILCHARD FISHERY. 29 inshore waters. A productive fishery, carried on within the comparatively narrow limits of the coastal waters, as is usual, appears to be based on a very finely adjusted cycle of physical and biological conditions, in which an extremely narrow margin is allowed for any abnormal condition, arising from the pre- ponderence or paucity of one or other of the given elements. The general results of the present season’s work, there- fore, tend in every way to support the deductions advanced in a previous paper,” but, although at this early stage of our investigations it 1s obviously impossible to define with any degree of certainty the probable causes governing the extent of migration of pilchard to the coastal waters of Great Britain, a consideration of the abnormal conditions of 1913 afford a basis of argument, such as might not have been forthcoming from a study of a succession of normal seasons. Briefly to summarise these considerations, therefore, we find :— (t) That certain biological conditions, which may usually be associated with the extreme south-western area of the English Channel, were observed in the coastal waters of the Cornish fishery area; a fact which might Iend support to a theory of an extension of suitable habitat for pilchards. (2) That in the same region phytoplankton, 7.e., food of a character undesirable to the fish, preponderated over zooplankton throughout the greater part of the season. (3) That in Scilly, and to the east of Plymouth, food of an eminently desirable character was largely in evidence. Passing now to the facts concerning the fishery, we find :— (4) That the migration of pilchards extended as far east as Deal, and that a profitable fishery was carried on within the near vicinity. (5) That the fishery was also of a productive character in Scilly. (6) And that it was not until an observed coastal visitation of shoals of Calanoid copepods to the waters of Mounts Bay early in October that the Cornish fishery became productive. 21 “* Mera No. 1,”’ 30 THE SCIENTIFIC AND ECONOMIC ASPECTS The above facts, considered conjointly, obviously lend some support to a theory that the pilchard seeking coastal waters, prompted thereto possibly by some obscure atavistic tendency, may, if suitable feeding grounds be not afforded by the waters in the immediate vicinity to its winter habitat, and providing that suitable conditions of sea temperature, salinity and density exist elsewhere, extend its migration beyond normal limits until a desirable feeding ground is encountered. PA Ea Esty INTC IE THE OccURRENCE OF SEXUALLY Mature PILCHARDS IN INSHORE WATERS. As previously stated in the foregoing paper, the pilchard habitually spawns at a considerable distance from land, the fish forming the object of the Cornish drift fishery are therefore either in unripe condition, or of the type known as “ shirmers,” 1.e., spent fish of somewhat emaciated appearance and above the usual size. Cunningham” remarks upon the fact that ripe pilchards are generally taken accidentally in mackerel nets shot twenty to forty miles from land, the catch seldom exceed- ing fifty. The period of time over which such fish are taken extends from the beginning of June to the end of October; they are commonest in July and August. The same author comments upon the comparative scarcity of ripe males caught in this manner, but omits to mention any exact data as to the usual area from which such examples were derived, beyond detailing one specific instance of the collection of eggs on September 5th, 1893, ten miles south of the Eddystone. All of our records prior to 1913 of the capture of spawning pilchards in mackerel nets lie on positions twenty to thirty miles south to south-west of the Wolf, and they are not numerous. From information derived from a fish curer at Newlyn, it appeared that a catch of five hundred ripe pilchards was made OF THE CORNISH PILCHARD FISHERY. 31 by a drifter shooting for mackerel about ten miles south of the Lizard early in June (1913). The same observer men- tioned that he had dealt with a catch of about two thousand in July, and that fish of this character had been very frequently through his hands prior to the end of August. These facts appeared to have impressed themselves on his memory more particularly owing to the difficulty he had experienced in cetting the fish to cure satisfactorily by the usual method of calling. Replying to our further enquiry, he stated that, to the best of his belief, the ripe males were in almost even propor- tion to the females, APPENDIX II. Nev Curinc By CREOSOTE. In the “Fish Trades Gazette,’ Vol. xxxi., No. 1606, p. 36, appears an interesting article dealing with the curing of herring and pilchard gear by means of “green oil,” 7.c., crude creosote, a practice which has been recently in vogue amongst the West Country fishermen. It appears that the majority of observers interested in the fishing industry, if not from the scientific from the enlightened standpoint, have regarded the innovation with considerable misgiving throughout the past season. As to how well founded these tears certainly were, is proved by the results of a series of experiments performed at the Plymouth Marine Laboratory by Dr. E. J. Allen. It appears that in a first experiment one part of the oil added to 100,000 parts of sea-water, and well shaken up, proved fatal to thirty healthy swimming prawns (Hemimysis) within an hour. In a further experiment one part of the oil was added in a similar manner to 10,000,000 parts of sea-water, and twenty-five specimens of the same crustacean were put in. One-half were dead in twenty-four hours, three -quarters were dead in two days; all were dead in five days. In both experi- ments sufficient aération of the water was provided for, and in a control experiment carried out in ordinary sea-water under similar conditions of aération, etc., no deaths occurred. 22 Cunningham, J. P., ( Mark. New Paghes 20, U7 2 2 THE SCIENTIFIC AND ECONOMIC ASPECTS Go It may perhaps be mentioned that medicinal creosote is soluble about one in four hundred of water, but the solubility of “green oil,” in which guiacol probably predominates over creosol, may be considerably less. When, as we have heard it described by Mr. Matthias Dunn, a freshly cured net is shot and one can see an emanation of creosote floating on the surface of the water, it is not hard to understand the natural result upon both plankton and fish situated in the near vicinity. For even if we do not admit that a toxic effect could be produced upon plankton in the open sea by such means, it is not hard to believe that the pilchard possesses sufficient intelligence to prevent it from driving headlong into con- taminated water. APPENDIX III. PILCHARD WITH REDUPLICATED Rays To CaupDAL FIN. On August 20th (1913) we examined at Newlyn a pilchard 252 m.m. in length, a male, caught two miles S.W. x S. of St. Michael’s Mount, which exhibited a malformation of a type approximating to another which we once before met with in a specimen now preserved in the Museum of the Plymouth Marine Biological Laboratory. Unfortunately the present example was “aad venient y destroyed, but referring to our notes upon the subject taken at the time, it appears that the specimen had a double complement of rays to the caudal fin. This characteristic had the effect of broadening the base of the tail to about one-half again its normal extent. - The fin itself was nearly double the width of that of an ordinary example at its widest part, but appeared naturally to slightly overlap upon itself in the centre. The individual rays appeared to be generally thicker throughout their entire length than is usual. A fisherman, questioned upon the subject, stated that he had, very infrequently, met with similar examples before.