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Biologist to the Biological Board of Canada Price 13 cents MARCH. 1918 UNIVERSITY OF TORONTO PRESS TORONTO M ^»4\f'' *-».-: »iK--4Jf'^^; I 8 We present herewith the first of what. It is hoped, will prove to be a long and important series of bulletins dealing With our food-flshes. There has been a steadily increasing need for a simple and accurate presentation of the facts that have a bearing upon each one of the various problems presence, by our fisheries. The many scientific repm Which represent great advances in our knowledge, of neces- sity contam too many technical d.^alls for the ordinary reader, are usually too limited in scope to show the p.oper relation of the new facts to questions of economic import- ance, and for these reasons do not fill this need. The in tention is to present in simple form to those directly inter- ested m the fisheries the principal facts which they should know m order to make the most of the fishery resources we possess, and these bulletins should prove of use not only for present need but also for future reference. THE BIOLOGICAL BOARD OF CANADA. "Hi»l V^^^J . ^-\\ '■ "■ ' '''■'" '■ -i-vi-ii ill! Ill- liiiii: iinm ihi' It.n ..i i-l.m.l- \.u ii.iMi.ll.m.l BULLETIN of the BIOLOGICAL BOARD of CANADA, No. Histories of New Food Fishes I. THE CANADIAN PLAICE BV A. G. HUNTSMAN. Biologist to the Biological Bo&ru of Canada Price 15 cents MARCH. 1918 t'NlVFHSirV OK liiKOVril PRESS TOKON ; o THE BIOLOGICAL BOARD OF CANADA. Professor E. E. Prinxu Chairnrar,. Professor A. B. Macallum Secretary-Treasurer. 009247iy INTRODUCTION. F^Vr^r""-''^ '^"'' " ^''''' "^'"' f"^ '' "Pi^J '^'^Pansio., of a^.r hsh..y mdustry. On. of these i. the necessity of making the most of every available fo.Kl stuff owing to the present .wld shortage On the other hand the increased utilla^r every resource .s an essential for the maintenance of our f na^ia cred.t and the payment of our national debt. Among o.r r ™e our fisheries are of great importance. It is frec,uently stat«l th u we have the greatest fisheries in the world, but how Xe true th may be as regards natural endowment, it is not true of the use tha we have made of them, and if we fail to make prope use . f ^t fisheries our heritage will pass to others. A large fi hincr I ' I ciose at hand along our eastern coast, but the gLt r pit . it not w,thm our ..rr.tor.al waters and is therefore open tc> the world If the proper enterpr.se is shown in continuing to develop this fehmg area we should be able to compete succeLfully with othe nafons for ,ts control because of our fortunate geographic pos on Improvements m the raethods of handling an'd t'ra n'sport^ he fish are however constantly nullifying the advantages we possess in the use of the most busmess-Iike and economical methods are necessary if we are not to lose this fishery Foremost among the points to be attacked in this e.vpansion is our failure to make proper use of certain kinds of fish that are obtainab^ m large quantities or that are taken as by-products n other fisheries and discarded. We purpose furnishing a se o accounts of unutilized fishes in order to show what kin.K are Hit 7, T '""' *''' "^^ *° ^"^^'^ "^"'-^-"- I" this ser I •t IS intended to present in simple form the results of our s,H.chl mves igations, the full reports of which will appear elsewhere The chief questions that we shall attempt to answer in these accounts are the following. '''' What is the most suitable name for the fish.^ How can it be most easily recognized.^ Where is it to be found .^ In what quantity can it be obtained.' How ran it best be caught? In what form should it l)e marketed? What size does it attain? What are its habits? What d(Ks it eat? How rapidly dws it ^row? Although it is (|uite ..bvious that these cannot be answered veral countries liste.l. England, -Long Rough Dab; Scot- and,— Lang Heuk; Ireland,— Smeareen ; Holland,— LangeSchar( = LongUab); Denmark,-Haaising (=Shark Dab); \orwav,-Ler- Hyndre( = Clay Flounder); Sweden .-Storgapen (= Big Mouth). I o our fishermen it is known as Sand Dab, Turbot, Flounder, Plaice or Phe (to many of the French fishermen), while on the Toro^n, markets it is exposed for sale as Flounder or Sole. The use of all these names means that this fish is constantiv confused with other kmds. for the term flounder is more often given to a v^ry difTerent kind of flatfish that is speared in shallow water, while a third species that lives in deep water and cannot take the hook because f.f its >mall mouth, alone should be called sole. We should undoubtedly use only one name for this h^li and that one should be both distinctive of the kind and also cjuite tree from objection. Since Plaice is one of the names alreadv in use for the species and not given commonly to any other fish in our waters It IS by far the most suitable one for general adoption, particularlv' m the trade. To avoid any confusion with other kinds, which are given this name in other countries, it would be well to prefix the adjective Canadian, and therefore we have used the name Canadian Plaice on our title page. RECOGNITION. The flatfishes are all easily recognized by the long fins, one along each edge of the body, as well as by the verv flat shape. «'...^ip^4u:ji tf^ ^ Sl. '■i.uA^7.mrifdifc>^BKaM&..Ju^ AmonK the flatfishes the plaice is like the halibut and unlike the Houmier and its relatives in having a very large mouth with well deve„pt-d teeth, the mouth indeed being so large that its angle is well back to the middle of the eye. Unlike the halibut it has along the middle of the body an almost straight 'lateral' line, which is without any arch near the head, and it differs from both the halibut and turbot m having the end of the tail rounded instead of concave or h.|llow. Finally the plaice differs from the window-pane, which also has a rounded tail and a large mouth, in having the eyes on the right side of the body instead of on the left side, and in not h-ivmg a distinct arch in the 'lateral' line near the head. It alone of our flatfishes has these three characters combined— /arj?c mouth almost stratght lateral line, and rounded tail (see figure 2) The Ne«rly straight lateral lioe Rounded tail Ku.. -I'laico fifteen inches long from Le Have bank, off Xova Scotia. After II. ■nouth L. Todd. colour, of the plaice is a uniform light or dark reddish-brown, although there is a series of from three to five dark spots along each side of the body. These are, however, usually distinct only in the young (see figure I), but occasionally they are to be seen in quue large and old fish. Another character that is familiar to any one that handles the fish is the very distinct roughness of the sur- face, which is caused by the small, but sharp teeth on the free edge of each scale (.see figure 11). ■^'mc':M ':^simi. DI8TBIBUTI0N. Where does the plaice- \iv,f The answer is that it is to In- found alons our whole Atlantic coast and to the south along the Xew Yo k, while at the north .t occurs as far as the straL. of Belle Isle an.l ixrhaps farther, though no records of its being c.n the outer «oast of Labrador have been published. It also lives in Greenland wat.r. and as a slightly different variety along the coasts ..f nort^. western hurope. As to the depth of the wat^r in which it lives there are records of . s havnig been taken in as shallow water as 5 fathoms at Ice- land and m as deep water as 350 fathoms in Davis strait Isu illv Hii.. •>. —Atlantic Coast with the ( ircles and crosses show tl pectix 'ly have been taken. pectix ly have been taken. "* ^"""^ -^""^ ""^ '^""^ °' ""c fry however u is found onb lepths of from 20 to 100 fathoms and -n hgure 10 can be seen ho e found it strictly limited to the deeper parts of the water between Cape Breton and the Magdalen islands At these levels is to be found during the greater part of the year the coldest part of the water, and in this it thrives It ranges frorri the deep harlKuirs and fjords alonR the coast to the outer fishing banks at the edge of the continent many miles trom land, in fact wherever suit.if)le depths occur. We have shown l)y the lined area on the chart in figure '.i the extent of the hottom on which it lives, and it is indeed very great. The circles show where the actual captures of the fish were made, upon which we have based our chart, while the crosses give the places where the eggs or fry have been taken. The correspondence is not i-xacl, since the latter are frequently carried by currents away from the I)laces where the adults live. The plaice seems to prefer to live on soft mud or fine sand, but is not strictly limited to such kir .s of bottom. It perhaps moves to a slight extent toward the shore in the cold part of the year and away from it during the sunmier, but this movement does not seem to be very distinct. ABUNDANCE. Towards the north the plaice is, after the cod, the most abun- dant fish occurring at moderate depths and the total quantity must therefore Ik? very great. We have made a provisional estimate of the amount available, which is based upon the quantity of cod landed yearly and the abundance of the plaice relative to the cod. They have practically the same distribution both in depth ;\na in extent from north to south and they are taken together on the fishermen's lines. Fifteen experimental sets of the line trawl were made in the gulf of St. Lawrence at various depths and times during the summer of 1917. Many of these sets were much more favour- able for taking the migratory cod than the stationary plaict. as they were made in shallow water that was only temporarily suitable for these fishes. We found the ctxl to be ten times as numerous as the plaice and to weigh twenty times as much. If now we take this to be the average relation between the two fishes, there must be fron even to ten million pounds of plaice tl-.rovvn overboard by the fishermen each year, for from one and a iialf to two million hundredweight of cod are landed yearly at Canadian Atlantic ports. If the plaice were marketed at current rates for the fresh fish, it would mean for the fishermen an additional revenue of about §300,000 and the retail value would be from one-half to one million dollars yearly. This estimate is based upon definite, though Iim.tf.1. nif„rmali(,n and .,nc is c. rtainly n.nstrvativt- in stating that sc-veral million pounds are lost annuailv. while a nuicli larger (luantjty rould doublk-ss be obtained if those spofs were fished where the plaice are most abundant. In 1915 Captain Thor Ivvrsen showed us a very large catch of plaice that had been made when tryni^, f.jr cod. and we have been informed by nshernien of (heir liaving made similar hauls. CAPTURE. The marketable fish, which are 12 inches or more in length, may I'e taken on the set lines or 'trawls', although thev take the h to 22J inches long averaging 14^2 inches, and weighed from 7 o/. to 4 lbs., averaging Ify oz. •Although a nine-inch fish is considered marketable in Great Britain, it is probably not necessary for us to make use of fish any shorter than 12 inches, although in the bay of Fundy a lower size limit will be necessary if any number are to be taken. For that region the limit is a matter of indilTerence from the standpoint of 10 ».mservat,on. smco .t ,s „,„ a successful spawning ,,la.T a„.l also since- tlu. Krcwth .,f tJu fish tlu-n- is very rapiix in.Iie>, a li.uit a, l.,w ,s nine inches will still leave a lar^e number ,.f spawi.Mi; fish. RELATION OF WEIORT TO LKNQTH. w..ilh/r'r * t •'"".■' '''"■''■ '''^'''"'' ''^•'^^■^ ""• ■'^^•'•■'K'' ^'■"•"i"" "f ^^ught t„ length in the plaice fresh fn.m the water. The weiKi,. after shipment is a trifle less. To a certain e.\tent the weight increases as the cube ')f the leiiRth, that is. if the len^lh is (joubled (X2). the weight is increased tc. t'i);;ht times tlie former .imouiil (X2'). This is not, how- ever, altogether exact, sinn- the shape of tiie lish changes with ajie, the width increas- ing more rapidly than the length. There is considerable \ari- ation in the weight of fish of the same length, as is shown by the fact that oni- 18 inches long, though prob- ably weighing 1 |b. 14 o/., n".e:ht weigh as much as 2 lbs. 2 (,z., or as little as 1 11,. ]() „z.. or even less if opened up and drained. Fii.. 4.- Ls'.gtK In in<:h«« -y i-raije rclalion of weight lo ItiiKth in the plaice. WASTE. As the head is small and the guts or viscera not bulky, there is less waste in the preparation of the plaice for cooking than is the case with most fishes. Also the arrangement of the llesh is r..ost convenient for eating, for owing to its p xuliar shape there is a (hick layer of flesh, entirely free from brmes, on both the upper rnfl the lower (really the right and the left) sides of the flattened backbone. 11 I w.lvi- fish from ]:\ to 24 inches in length and from 10 ../. to 5 H». in wfiuhl w«Tf [)ri-pand without any .itti-nipt ff) rHain a larm' prn|H.rti<>" of lUv wiinht. Tfu- hra.l. kiKs. fins, and scak-s wm- rimovfd and the Innly washed. The weiRht after preparation ainoiniled to alxnit tlO' ; . as an average value. .)f the wei>;ht fresh from the water, and if fish from the market had luen t iken. the pro|K(rtion would have k-en still greater. PALATABILITT. The plaiee is sweet .md of fine flavour, is not oily, l.ut r.ither similar to the lloiuider or sole. thou«h having a distinetive texture anci flavour. Although ii..t th«- same, it is as n.-arjy like the fJritish I-laice as is any fish that we li.iw. We have eaten it at the co.ist and aJM. as obtained in the Toronto markets and consider it e.xellent. It will un.louhtedly win a pl.ue ol its own on our markets, if only It tM- made ktiowi; and a sufficiently l.irge supply furnished to meet the demand that is created. SEASON. It is suitable for use throughout the year, se-eing th;.t i^ lives in Mich cold water, hut it is in better condition in the fall and winter after the season's growth and before the spring si).uvning condition IS reached. Also from the standpoint of shipping conditions the coUl part of the >'ear is preferable, but from Drember to April ii will not be possible to obtain it in the gulf of St. Lawrence because of the ice. although to the south it will usually be possible to get it at any time of the year. MATURITY. VVe have not been able to find out as definitely as we could wish at just what size the plaice first becomes ri|K'. since one spawning seascm was over before we began this study and the next has not yet come. Fulton, and ilso Holt, found that the Kuropean variety becomes ripe at a length of about six inches, both males and females. Of fish taken in Passama(iuodd\ bay in the fall of 1017 .some of both males and females were beginning to be ripe, but none shorter than five inches were becoming at all ripe. Those five inches long at that time would probably have reached a length of six inches on tht> arrival of the spawning season of 1918. 12 OirmiNOBS BITWIIM THE 8EXIB. I hi- (wo sfxes an- so miirli alikr that an fxaminalioii «.f the inU-rnal <,rKan> is usually mrrssary n ord.r l<. find out win thir tin- fwh in «|Ufsii,m is mali- or fi-malr. ( )m- tlu-n tnuls, en cxamininK lar^f nunilwr^ of individuals, thai tlu- nial.s do not riMcli m, lar-i a si/f as thf fiinak-s. for. although .hiring tin- first ftw v.ars of li?i- tht-rt- is not nuuh difrfroncf bttwf.ti tluni in tlu- rati- of Krf)\vtli. when they l)fconu- niaturf. the inaU- yrows more slowly than the fttnak-. This is not the only reason for the strikinx latk .)f lar^e male-, sincx- a study of fish of different ages shows that for the »ir.,t two or three years there are more males than females, hiit thai th. «.lder the fish In-come the smaller is the relative numk-r of ,nal. ., and usually females alone are found amonR the oldest fish. In the gulf of St. Lawrence. • ' re there arti fish nf main slow growth and late maturity in cold water. FERTILITY. Like most fishes the plaice is extremely fertile and sheds many thousands of eggs during the spawning period The actual numk-r of eggs varies greatly, but Fulton found from liO.OOO to 60,000 in 13 •IxriiiK the lif. .,f . ft I „ •'"•'*""'•'' ''"■">••'' "'""l-rspawm.l 8PAWNINO. .-. ..f N,.w„„ , , n'„.'i :;:.r:;;';;" "• '"-r. J"'^ ■■•' ••'^■ rhiTf IS nothing to show tint il,.. „i • "H'"i!< .m Mij{ht. mt tggs recently laid were near the top of the water. DKVILOPHIirr. When the egg. which is largely yolk beirir>; r^ A., i .vmg n^atter collects at one Mde%nd'f:lst' UtV^'^Se';;' -). n.ak.n. that side heavier so that it is a.wayl und^Lt^.Th^ It ,'.<, v^--<- l-li..ii. l-r\ om- iiiiartiT iil .in inch liinu anil almul llinr »i-ik- nl.l. laiiKlit in tli.- unll III Si. I,:nii.nci-. I'lioiiiuniphi'il l>\ I'ron rAiiiliMvui l-n.. 7. l-'i> rliv. n-l«i-nlirths ,,| an in. h limi; anil alioul t»(.ai"l Dtii-liall nuinlli^ nlil . anuht in tin- unit c,i St. I.a«rcii.i-. I'liotnmaiiln-.i In I'roli-sMir .Xnrlit-a.n. I"ic. s. l-'r\ -c%( n-imhlliv 1,1 .III |]i,|| liiTiy and alxint linir iniiiuli- ..Id. .auulit in tin unit ..1 SI. i..iwiin(i', I'hotouraiilu'll liy I'ri>lr>s(ir AniliT-am. I-'ii,. tt. \'ininu iilaii 1- t\Mi iinhr> ioln: aMdaliiMU t-mht niiintii> nlil. Ill Knn(l\ . I'}ii>tin.:raiiln-il ti\ l*ii'lfv>iii \nilirsiui. lixinj; matter dividi's many times, forming a lar^o numlxr ol livinj; units tir iclls, which spread in a thin sheet over thi' lower surface' of the e^jj and gradually extend upwards so as to encloM' all the yolk. When this living sheet has half covered che egg, a thickening appears in it, stretching from the edge toward the centre at the lower pole of the egg (see figure .%). This is the beginning of tin- l)ody of the future fish and it becomes steadily longer and more distinct. One end, the head, is soon seen to Ix' larger than the rest and in it the eyes appear very early. The smaller tail end lengthens very r.ipidly and grows away from the surface of tlie egg (see figure .W). At an early stage it acquires a delic.ite fin niembnme, whii-h extends along the lower surface and around the tip of the tail to the upjx'r surface, where it continues almost to the head. The CI louring matter, which is chiefly black, appears throughout the bo«ly and tail in scattered branched cells, and later collects to fornt more or less complete bands across the tail, which are arranged in a fashion peculiar to this fish (see figure ne), there Ix'ing four, of which the first is incomplete above. During this growth the volk has l)een used up to form the living matter and the muscles have develojK'd on each side of the ta I and body until the movements ot the tail are strong enough to break the weakened egg membrane and allow the fry or larva to escafx' into the seawater. FJy this time the mouth opening has apfwared beneath the head, and, since the yolk has been used up, the larva must eat in order to keep on growing. At first it feeds upon the minute plants called diatoms, which fioat in the water, but as it lx;comcs larger and more active it captures and swallows the small shrimp called copepods, th.it are so abundant in the water and form the 'red feed' of the herring. It has the curious habit of keeping to a depth of about ten f.ithoms during the day and coming to the surface only at night, probably lx>cause it is repelled by the stnmg light of day. The older it gets the deeper it goes into the water during the day, until finally, as we have observed in the gulf of St. Lawrence, it is far from the surface even at night. Whether this is due to the surface water fiecoming warmer or to the older fry preferring the deejjer, colder, and darker water, we do not know. The larva, which on hatching is only about one-fifth of an inch in length, does not grow very fast, but it soon takes on a very difTerent shape, becoming much deeper and flattened from side to 15 weMas i'i' h?T '\'^" .""P^'' W'-^') and lower (anal) fi„.s us Hell as ,n the tail and pa.ree figure 7). It is nnlike the adu t fish n hay.ng an eye en each side of the head and in swiniminrupXh" jn the water n,stead of lying upon one side, but when it re."ch2 arSs^ 17" ""' '■'"' ' '''''' '' ^'^- '-•-' ^--^« i" .rowing:;: eye see hgiire 8). This ,s the metamorphosis or change from the condmon of the arva to that of the adult. At about fill; ops sw.mmmg freely in the water, goes to the bottom anck"; I/ainf . K "'"'' ''' ''' '^''^ "'^P^^'"-^ -d the blind ift "d"^ agamst the bottom. At this stage the colouring matter k-comes more abundant and develops only on the right side, the left sTd' remammg colot,rless. A young individual that has on K recLntt changed from the lar^•al condition is s.. wn in figure 9. Figu" , Arrows .ndicate the direc,.o„ of mol^rnem orof'^de^lopmem^ ''•'" '"" "'^"^ ' illustrates the life history of the piaice, as we have descrilx>d it In he southern part of the gulf of St. Lawrence spawning takes inromT'"'. r.' '"' ^r ^"' '""^ ^'°""^ '^y '^^^^h'from the c^g m from two to three weeks after the latter have been shed Their growth ,s very slow, amounting to only a quarter of an inch a montn so that by the end of August they are about an inc ong and before wmter nearly o- ^uite two inches in length. The growth or the first year .greater in the warmer waters at'the south.'wh" a length of more than three inches may be reached before winter sets m. "•iiiv.i 16 R-iTi. ■.'■■■■ "•'V 4 I I BEEEDINO PLACES, ETC. spawn a 1 wa ers >n which the adults live are „..t equally suital.le as breedmg places, for .ome n,ay lack suitable ccnclitio., " t r for the development of the eggs «r for the growth of the frv We hav^ been found, on the Newfoundland banks, on the outer hankl Ih It TT """ ^'"'" '■^'^^"^' ^'""S *he coast of .V,.va Sco ifir P^ I, , •^'^^^"""^'^"d, Labrador. Anticosti. (laspe Prince Edward ,sland, and Cape Breton island). In the bay o Ku "l v and m Passamaquoddy bay eggs are spawned and devdop a k" part,any. but no fry have been found, so that the conditions ^r must be unsuitable, perhaps because the heavy tides prevent the nvers into he sea, from accumulating at the surface in the spring by keepmg .t m.xed with the colder, salter water below. The 'ok lil,n "M" ?"" ^"''" ""^* ^^•^^ "^ "^^P^ "P hv the old., f y .vmg m the deep water teing carried in from the gulf of Ma. e In the deep currents and distributed over the bottom in the l.av of Fundy and Passamaquoddy bay. " The eggs and fry. which float or swim more or less passively in he nla"' "h "T'^'u '^""''^ '^>' '""^ ^"--^^ -anv miles f on. he places where they have been spawned, so that they are dis- tributed far and wide. For the most part, howev.r, the eggs ,x - .cularly the early ones, will be found near the surface jusf al e he sp<,ts where the old '^sh are. and if we haul a fine n t through the water at the surface a. the right season of the year at any s™,t n the sea we can easily find out whether or not the'e are any p£ m the neighbourhood and how abundant they are. Their eggs may be qu.te readdy distinguished from those of other fishes even with the naked eye by the.r comparatively large size an.i by the presence ill: ':;5dr^ "-'-^ '- - --^ -<■' ^^^^^^^-^^ theiTr "'"^7 ^""^ ^^^ '" '^' '^''^ ""'^ ^•'^*^'- '-'"^l "^-^'fore when u uT "/^transformation comes they reach the very bottom in w .ch he old f^sh live and do not live in separate regions whi might be called nurseries, such as are to l>e found in the case- of 17 I >r tnur lurther .levelopment and growth. It would be nu.«f seek tho lu tt u ^ ^^'-''" "P *° tf'e fme when they muj rom our present knowledge he considereS inadvisable t the pla.ce l,ccomes sufficiently valuable, it may prove worth wh.Ie to undertake to transplant it from «v.rpo7u ated arc" those, where .t ,s rare or from which it has been fished out ^ has already lx>en done with some success in E-irot^L T r '" "'" »">■• '^■<»"-«-- e found in its stomach ^thT^hih ''^^P^'"^''P^' and b,Kiv' ca4v ,„,! '"'" "'""^ ™undw,,rms in ,h.. i„,c„i„e l-etwoen 'he I'ipl *'."'" """"" ™"P«'1.««1 -lislomc. of ^z tar,:"':r ''';;"::' * ^f -' ^' ,'-™- "«" CLIMATE. 19 Tf^rr^ the water, it has been found in water that is quite salt, containing from 30 to 34 parts of salt per 1,000, although somewhat greater or smaller amounts are quite possible. The eggs and young fry will usually be living in water containing less salt than that m which the adults stay. RACES. Fishermen Iwlieve that there are different varieties of many of our sjiecies of fi.-ihes, and speak of Quoddy herring, Labrador herring, etc. Often distinct differences can be found in fish of the same kind, but from different places, one variety being deeper or thicker than another, or there being differences in colour or in average size. These characters are not very good for exact study, as they are apt to change with age or the condition of the fish. It is better to take characters that do not change with age. such as the number of rays in the fins or the number of parts in the back- bone. If constant differences in these are found we may Ix; fairly sure that distinct races exist. The rate of growth of the plaice varies with the locality, but the chief cause of this appears to be the temperature. There are, however, other differences. The average number of rays in the longest fin (dorsal) is higher in fish from Passamaquoddy bay than in those from the gulf of St. Lawrence off Cheticamp, and in those from the Bay of Islands, Newfoundland it is still higher. There are just as distinct differences in width, although in this case the size must be taken into account. These from the gulf of St. Law- rence are the broadest and those from the Bay of Islands the narrowest. For example the average width of plaice ten inches long would Ix; — gulf of St. Lawrence, three and eleven-sixteenths inches; Passamaquoddy bay, three and three-eighths inches; Bay of Islands, three and one-eighth inches. We have therefore fairly distinct races of plaice at different points along the coast, but we do not yet know how they compare with each other in quality. LENGTH OP LIFE AND RATE OF GROWTH. The age of a fish may usually be found by examining the scales or the small flat bones from the ears (otoliths), for rings on these indicate the seasons through which the individual has passed, just 20 r:v '1 't .. -kr^^^^ as in the well-kn„wn ca.sc- of a cut through the trunk ,>f a tree, in which the CHintuiK <'» the rin^s gives the a^e ..f the tree in years. ' ■ own in tigure 11 it will I.,- seen that (he broad In the scales sh m. end r.f the scale is fringed with teeth, like the teeth of a comb A short part of this end of the scale is the only part uncovered and free when the scale is still in the skin of the fish, the remainder Ixin.. covered by the other scales just in front. The covered part is marked by many parallel lines, which are roughly in the shape- of half circles, the centre of which is a point— the centre of growtii— ]ust mside the middle of the toothed end of the .scale The lines which are called circuli, are partly distant from each other and' partly crowded together. The plaice begins to grow in the spring at a rapid rate as soon as the water starts to warm up. and this rapid growth lasts during spring and earlv summer. In the part of the scale formed at this time the circuli are far apart In late summer and m autumn the growth of the fish gradually lessens and the scale formed during th". slow growth has the circuli close 21 fo^H'thtT. Finally diiriiij; the winter, Rrowth of l)oih fish and scale practically stops altoKethcr. I'Iil- vd^v of the scale cJiirinR any winter is therefore the line where the circuli chan>;e from a closely crowded condition (autumn ^Towth) to a widely s«()arated con- dition (si)rinK growth), and we can thus s»v on the scale more or less clearly the succession of spring', summer, autumn, and winter for each year of its growth. The scale on the left of t^^ure 1 1 is from i i)Iaice seven and a half inches long, which was caught in Passamatiuoddy Itay, N'.B., in OctolxT, lOi". It has two bands where the lines are dose together, one near the centre of growth, and the other along the edge of the scale, and it has therefore lived through two autumns, the second of which is not yet over. Between these two hands is a broad area with the lines far apart. This is the growth of the second spring and summer. Where is the growth of the first spring and summer, for there nuist have been such, seeing that the eggs are spawned and hatched in the spring? It should Ix' Ix'tween the centre of growth and the band of the first autumn. The reason it is not there is because during the first spring and summer the fish was at first an embryo in the egg and after^vards a larva or fry. In both of these stages it is (luite without scales, which begin to grow only when the left eye moves over to the right side of the hcas to the bottom to live. This does not happen until the slow autumn growth has begun, at which time the fish is already one and a half inches long. The scales therefore show no trace of the first summer's growth and indeed some scales may not l)egin to grow until after the first winter. The fish to which this left scale l)elongs must have been nearly two years old in the fall of 1017, which means that it was spawaied in the sjjring of l!)l(i. The scale on the right in figure 11 is from a fish a little under .se\en and one-halt inches in length, which was caught in the Bay of Islands, Newfoundland in August. 1915. Although smaller than the other fish, its scale shows six bands where the lines are do.se together, which means that it had lived through si.\ autumns. At the edge of the scale the lines are far apart, showing that in August, lOlo, it was having its seventh spring or early summer growth, for at that latitude the summer in the deep water is very late. Although smaller than the .six'cimen from Fassamaquoddy bay, it was more than three times as old as 22 the laftiT, so rcmarkalilo is tin- ffft-rt r.f n.ld water as compared with warm w.iter (»n the growth of this fish. It is possible not only to tell the a^e of a fish from the Males, but also to calculate approxinial.iy the amount of ^;r,,wth in each year of its life. VVe first find out the corresix.ndeiice in rale of growth Ix-tween the scale and the whole fish In j,'ettinn the awr.iij,. size of the scale in fish of ditTerent lengths. Then on nuM>urin>; the distances between successive winttr points on the sc .de we can calculate the amount of prowlh in len^'th of the fish for corrcspmid- niK years. This also gives us the length (.f the fish al each vear of its age. In this way we have found out that in Passama<|uoddv hav with a temperature at the bottom as high as 50° f'. in the Lite summer the plaice reaches a marketable size (12 inch»s) in fn.ni three to (iw years, in the open bay of Fundy with a temix-rature as high as 4t)° V. in from four to six years, in Chedabucto bay (temiHrature probably up to 38° F.) in from six to nine years, in the gulf of St. Lawrence about halfway bttwe«'n Cheticamp and the M-igdalen islands with a temjK'rature not above 35° F. in from eight to eleven years, and in the Bay of Islands, Newfoundland, where the uni- perature never seems to go above 32° F., no marketable fish wen- found, but the rate of growth shown by the small fish captured would mean that from 10 to 13 years would Ik- recpiired to priKku e marketable fish. Figure 12 shows the average growth of the plaice in each of du-se waters, the successive years in the life of a (ish l)eing marked otT at the bottom of the figure and the height to which the heavy line for each locality rises for each year showing the average length reached at that age. To what this amounts in inches is shown on the right side and in centimetres on the left. The steeixr the rise in the line the mf)re rapid is the growth. The growth is most rapid in f'assamaquoddy bay, where a length of 15 inches may l>e reached in less than five years. The slowest growth takes place in the Bay of Islands, where the plaice are little more than five inches lo.ig at the end of the same length of time. Temix-rature is therefore a most important factor in the growth of these li;,lies. The important thing, however, is the production of nuirkei. fi.sh of large size. Neither the very warm nor the very cold water are best from thi.s standpoint, for in Passamaquoddy bay, although 23 the growth is \iry rapid, llu- diaili rati- is >{r()Wth is so stunted that it may U' doubted whether any individuals reatli any C()nsi(Ura!)le size. Apparently the (ish that live lonKfst and U-eomc 0 s la is 10 i4ge in Years. I'll.. I.' -Curves illustrating tlie rate ol growth cf th.' plaice in different regions. the largest are those in waters of middle warmth. We have shown this condition in the figure i)y the fine Une which gives a growth to a lengtli )f two feet in twenty-two years. This is the 'optimum ' or iK-st growth of the plaice. 24 Th«- lim-s in thi- fiKuro ^iw flu- iiwr.iKf growth fortirli Im .iliiv In fiu h pl.iii' xinu' tiHht>. urow rapidly .ind sunu- ^lo\vl\ , to ".mmu extent tx'rau> not the >.inie e\rrywlu rr (ilitar\ nidi\idiial Imm this hay showed a growth tiearh as rapi,im.i(|ii(iddy \m\. In most regions some hslu - it li-.i-i will lie li\in^ where they liav«' the Inst growth, not Iiowim r ni Passam.Kiuoddy l>ay since owiiin to the luavy tides ihc vslmlr Iiih|\ of water reaches nearly tl same temjKrature, nor jKrh ip- in the Bay of Islands since the side )f such a deep fjord ari' too stu p lo nive suitaMe bottom at the def)lhs where the temix-ratiire i^ Im -i. Speakin}{ K^'t^Tidly the Ust place> for the jjrowth of thi- lisji arc the outer coast of No\a Scotia including the outer lishint; hank-, and parts of the jjulf of St. Lawrence, anil in thes»- wat«rs the U -i fishery is to Ix- exiKCted e\cept where they are ( ri)wdid out h\ oth»'r fishes. What is the greatest age tli.it the pl.iice reaches,-' It i- c'Ti.iiiil\ able U) live as lonn as 24 years .md proh.ihly M) \iMrs >hould U- assij;ned as the upper limit, I'nlike man it continues to i,'row throughout life, the ienjjth increasing up to the tinn' of de.iili. There is nothing to show when the f.ictor of old .ige come- in lo assuie death. It is very important to know how nuich the lisli g.iiii'- in wt iyhi each year, for from the standi)oint of food we are more iiitcri'-li-d in knowing how muih a fish weighs than how long it is. We (in readily find out the gain in weight, sinie we know the ye.irly iarrei-c in length as well as the rel.ition iK-tween length and weight ( figure 1 1. From these we have calcul.ited the \early gain in weight h r llw average growth in Passam.iquoddy hay and in the Bay of Island-, as well as for what we havx- called the 'optimum ' growth. I"igiiic |;{ shows the result in a graphic manner, in Passamacpiodd)- h.iy the amount gained in weight annually increase's very rai)idl\- from ye.ir to year until by the fifth yar 11 ounces are gained. In the Bay of Islands the annual gain is scarcely half an ounce even by the seventh year. The 'optimum' growth shows a steady incre.isf in the gain in weight \w.r year, which finally amounts to as much .is in the fifth year in r.issam;u|uoddy bay and the total weight of thr fir-Ii U- rc.nu's viry Kriai. Ihi- inrroasf in tlu- Rain, that i>* shewn, is not quitf n-Kular .•«(»•< ially in tht lattr yiarv This is partly diu- to th«- (lifriiulty of ni.aswrinK the linRth of the old lish accurately enouRh. for a very small mistaki- in measurement makes a bi^ mistake in the calculated weiKht. We can. howewr. dejK-nd upon the -i-neral Yeiri oi I.ifs. hu.. |:i. -Thr yraily Kain in Mcmht in oiirnrn for diffirrnt rcniodM. ■MtA increase in gain shown IninK substantially accurate. We may con- clude that the older the i)laice gets the more valuable it is as a machine for conxerting animals like the sand dollar and sea urchin into food sf'talile for in.in. DEATH RATE. During the first year while the fish is in the egg and fry stages, the death rale nuist l)e very high, so high indeed in the bay of Fundy and Passiui'a(|U(Hldy bay that apparently not a single egg hatches out. Because of the sm.ill number of old fish in this region wry few eggs are to Ix' found .ind of these none seem to reach the last stage previous t<) hatching. In the gulf of St. Lawrence on the other hand the conditions arc more favourable and a high percentage of the eggs, which arc very abundant, hatch. The fry are likewise numerous, but much less so than the egg:;, there being one larva to 10 eggs, certainly no more. The older fry are still fewer in number, so that onK- a fraction of the young spawned each year cwt change into the adult form and reach the bottom. We will consider the death rate of the adult fish in connection with our discussion of the stock. 26 THX STOCK. It hiiH Ijccn a matter of oxjKrurue for a nuruUr of years th.it lar>;i- plain- an- wry rare on the New Bninswick shore .»f thi- bay «if Inindy. So true is this that were the net trawl not used the fish would Ih- o)nsiderecond year and fewer of the older fish than would Ik: exfK-cted with such a death rate. We are quite coisi-rvative in concluding that the death rate in Passamaquoddy bay is at least 50%. We have shown this graphically on the right hand side of figure 14, where wv have represented successive years by horizontal lines placed one above the other, the relative numlnr in each year iK'ing indicated by the length of the line. The thick part of each line shows the relative nuinlxT of each age actually found, while thi' parts iK'lween the two curved lines give the relative nunil)ers in lin- stock when the death rate is 50% or one-half per year. The corres- pondence between the two is quite as good as could Ik- exjucted. A plaice has indeed a very small chance of reaching an age greater than seven years in this bay and in fact wc have up to the ()resent found, with a single exceptitm, none of greater age. The stock in the gulf of St. Lawrence is quite difTerent. 120 plaice captured in one haul of the net trawl at a depth of 30 fathoms halfway iK-twecn Cheticamp and the Magdalen islands in Sep- temlKT, 1017, were of the following ages: Age in years Number of plaice : 3 AH 1 4 5 I ..11 7 8 8 0 4 13 10 II 12 13 11 0 <) 7 j^l!) 120 1 i 1 Age in years Number of pl.i >e. 114 hi 15 !1« I V i 3 !l7 1 3 18 2 21 !22 ,23 124 0 I I i 1 i 1 Although for the many ages represented the numl)crs are too small to give the best p'cture of the conditions, it is (juite clear that then" is a \erv gradual decrease in the numlwr with age. As the proportion of older fishes is so high, the death rate in this region 28 mmmm mmmm Iml^t 1k' coniparativt'lN- low. On tlii' left liand sidf of fijjurt' 14 we have drawn curves to sliow the eoiiditioii of tlie stock when tlie deatli rate amounts to 12|/,' (one-eighth) of the total population |HT year and we ha\e indicated in till' thick lines thf luunlH-rs of ia('h ye.ir given in the table. The agreement is clos<' enough to warrant us in concluding th.il the deai'i rate in this part of the gulf of St. I awreiue is very nearly 12.'.' ,* [nr year, that i^, oidy one- (|narter of tiiat in I\issama((uoddy hay. It m,i\ he mentioiud that in this case l)ecause the growth for tlu' \-ear li.id little more than i)egun we ha\e madi' the ages k'ss 0'>' t"iir months) than what they were, insteail of greater as in the previous case. The ah.scnce of any- fish under tlirei' \ears in age is accounted for !)>• their vt-ry small size, due to slow growth, iiermitting them lo escape ihrough the meshes of the net. We liave heen ahle to study the ages of 77 plaice from ("heda- hucto ha\ , an intirmedi.ite region, which were examined in the sho[) of the Wm. I)a\ ies CompaiU' of Toronto. The luimlK-rs of ihi' v.irious ages that were tound are as loilows: .Age in \ears ... NumlK-r of ])laice . (i 7 S '.» 10 1 12 hi II ! ". It) 2 .'12 10 10 17 ( !0 ■I :; i 1 1 In this case also we have a rather gradual decrease in nunilnTs with age. which mians a low (k.itli rate. The earl\- years are not represc-nted, since plaice of tho.--e ages were too siuall to 1k' marketed, and if caught were not si'iit in. The age is given as five months greatiT than it actually was. The rate of decrease in mimlMTs with age is more rapid in this region tiian in the gulf of St. Lawrenci' and les'- rapid than in P.issama(iuodd\ ha\ , .md corresi)onds witli a death r.ite of ahmit 2.")' (,, (one-fourth) of tiie total |)opiilalion [XT year, ,i< we iiave shown in the middle of figure 1 1. The maximinn age reached in this localit\- (Hi years) i- likewis*.- intermediate lx!twei'n that for l'assama(iuoddy hay (ii \ears) and that for the gulf of St. Lawrence (24 years). Owing lo the more rapid growth in the warmer water the ilififer- ences in maximum size reached 1)\' the plaice in thi'.se thre<.' regions are not so great as would Ik.- expected from the ditferences in death rate, and are as follows- -Passama 1.5 at the left ('original condition ')• 30 'jes. It will Ix^ seen that each line IS one-seventh shorter than the one immediately Ik-Iow. Let us now suppose that fishing liegins and that after a seventh of each age have Ijeen removed by natural means, one-fiiiarter of the remaining marketable fish arc captured by the fishermen. Th'.- removal of such a large proportion of the stock is not at all unlikely, for by two methods of calculation it was found th.it that pn.portit'.n' of the total stock in the Xorth Sea was l)eing removed each vear by the fishermen. The effect f)n the stock of this intensity of'fishing for one year is shown in the second part of figure 1.5. The munbers Fm. 15.— The effect of fishing on the stock. TlSfvart flikiitg. of each age with the exception of those that have just attained the age of 5 years, have been decreased one-fourth. The conditions after fishmg for 5 and 15 years respectively are al.so shown in the figure. The progressive decrease in numbers affects chiefly the older fish, but it entirely ceases after 17 years, by which time a new stationary condition has been reached, one characterized by very few old fish compared with the younger ones. Also we find that the average size of the fish captured becomes smaller vear by year until the new stationary condition is reached. This effect is the more marked (1) the more intense the fishing, (2) the greater difference in size between the years, and (3) the greater the numlx-r of years represented among the marketable fish. Those who have fished the lobster during the last half-century can testify how definite this effect IS. It IS unavoidable and not due to any failure in the supply of young fish. The relative numbers of tne various ages would not be changed no matter how large a number of voung fish were pro- duced, although the total quantity of fish obtained would be 31 greater if more young fish were spawned, that is, there will be more fish but just the same sizes as before. The only remedy is to stop fishing in whole or in part, and full recovery will be reached only after fishing has ceased for the same number of years as are repre- sented in the stock of marketable fish. Whether such stoppage may be desirable or not, depends upon so many circumstances that it is not worth while discussing the matter here. If a very thorough fishery for the plaice is begun, a marked decrease in the awrage size of the fish taken is certain to occur in the course of a few years, because the marketable fish are of so many different ages in the most important parts of our waters, and, since the plaice moves about so little, each locality will show this effect very quickly. The fishermen can easily increase their catches in such an event by seeking new grounds. SUMBIASY. The plaice is abundant and generally distributed along our whole Atla itic coast at depth.s of from 20 to 100 fathoms, but may best l)e fished in the southern part of the gulf of St. Lawrence and on the outer coast of Nova Scotia. It is already taken in rather large numbers as a by-product in the line fishery, although not utilized, and it may easily be taken by the net trawl. It is of good size and of fine flavour, being in the best condition and shipped most easily during the fall and winter. For years it has been sold in the markets of the American cities and is now finding a sale in Canadian cities. The supply in our waters has as.yet scarcely been touched, and it is estimated that several million pounds may be obtained yearly, but if the fishery is at all intense a certain diminution in the quan- tity and the average size is to be expected. It is most desirable that this fish be handled, advertised, and sold under the name of Plaice alone, so that a permanent demand may be created for it as such. It should not be called flounder or sole, since, these names are more commonly used for other fishes that differ from it in appearance and quality. 32