Reared on the Pacific Biological Station Experimental Fishfarm

Transcription

1 The1975~pfSabnn Reared n the Pacific Bilgical Statin Experimental Fishfarm by w. A. Kennedy, C. T. Shp, W. Griffien, and A. Slmie FISHERIES AND MARINE SERVICE SERVICE DES PECHES ET DES SCIENCES DE LA MER TECHNICAL REPORT N. 665 RAPPORT TECHNIQUE N Envirnment Envirnnement Canada Canada Fisheries and Marine Service Service des peches et des sciences de la mer

2 Technical Reprts Technical Reprts are research dcuments that are f sufficient imprtance t be preserved, but which fr sme reasn are nt apprpriate fr primary scientific publicatin. Inquiries cncerning any particular Reprt shuld be directed t the issuing establishment. Rapprts Techniques Les rapprts techniques snt des dcuments de recherche qui revetent une assez grande imprtance pur etre cnserves mais qui, pur une raisn au pur une autre, ne cnviennent pas it une publicatin scientifique priritaire. Pur tute demande de renseignements cncernant un rapprt particulier, il faut s'adresser au service respnsable.

3 Department f the Envirnment Fisheries and Marine Service Research and Develpment Directrate Ministere de l'envirnnement Service des Peches et des Sciences de la mer Directin du Recherche et Develppement TECHNICAL REPORT NO. 665 RAPPORT TECHNIQUE NO. 665 (Numbers in this series were (Les, numers dans cette serie furent issued as Technical Reprts f the Fisheries Research Bard f Canada. utilises cmme Rapprts Techniques de l'ffice des recherches sur les pecheries The series name was changed with du Canada. Le nm de la serie fut change reprt number 457.) avec Ie rapprt numer 457.) THE 1975 CROP OF SALMON REARED ON THE PACIFIC BIOLOGICAL STATION EXPERIMENTAL FISHFARM by W. A. Kennedy, C. T. Shp, W. Griffien, and A. Slmie This is the 262nd Technical Reprt frm the Research and Develpment Directrate Pacific Bilgical Statin Nanaim, British Clumbia Ceci est Ie 262em Rapprt Technique de la Directin du Recherche et Develppement La Statin de Bilgie du Pacifique Nanaim, Clmbie-Britannique

4 - ii - ABSTRACT Kennedy, W. A., C. T. Shp, W. Griffien, and A. Slmie The 1975 crp f salmn reared n the Pacific Bilgical Statin experimental fishfarm. Fish. Mar. Ser~ Res. Dev. Tech. Rep. 665 : 20 p. Grwth and attritin are recrded fr ch, pink and chink salmn reared first in freshwater tanks then in seapens t 300 g in a pilt-size, cmmercial fishfarm-like peratin. Vaccines dramatically reduced mrtalities frm furunculsis and vibrisis. Piscine erythrcytic necrsis was recgnized as a serius disease f pink salmn in seapens. Predatin by tters was prevented after heavy initial lsses. -' -' RESUME Kennedy, W. A., C. T. Shp, W. Griffien, et A. Slmie The 1975 crp f salmn reared n the Pacific Bilgical Statin experimental fishfarm. Fish. Mar. Serv Res. Dev. Tech. Rep. 665: 20 p.." On a bserve la crissance et la diminutin du nmbre de saumns ch, rses et quinnat ~lev{s d'abrd dans des reservirs d(eau duce puis dans des cages en mer, jusqu'a btentin d'un pids de 300 g, dans une installatin cmmerciale de taille pilte du type piscifacture. La vaccinatin a prvque une reductin spectaculaire de la mrtalite' due a la furnculse et a la vibrise. La necrse erythrcytaire du pissn s'est revelee une maladie grave du saumn rse eleve dans les cages en mer. Apres de lurdes pertes, n a reussi a prevenir le pillage par les lutres de mer.

5 - iii - ACKNOWLEDGEMENTS We welcme this pprtunity t acknwledge the extensive help and clse cperatin given t us by clleagues bth within the Aquaculture Prgram: Drs. J. R. Brett and W. C. Clarke and Messrs. J. E. Shelburn, J. M. Blackburn and W. Damn, and in the Fish Health Prgram: Drs. G. R. Bell and T. P. T. Evelyn and Messrs. G. E. Hskins, J. Ketchesn, G. Traxler and Mrs. L. Hulstein.

6 - 1 - INTRODUCTION This reprt deals with the secnd crp f salmn t be reared n the experimental fishfarm at Pacific Bilgical Statin (Kennedy 1975, Ryan 1975). Fllwing the cnventin f earlier reprts (Kennedy et al and Kennedy et al. 1976), "1975 crp" means fish frm eggs that were spawned in 1974, hatched in late 1974 r early 1975, became fingerlings in 1975, and attained market size (abut 300 g) in The experimental fishfarm is perated: (a) t prvide data fr assessing the feasibility f cmmercial fishfarms in the marine envirnment; (b) t reveal bilgical prblems related t cmmercial fishfarming under lcal cnditins; (c) t cntribute t the slutin f such prblems; and (d) as a medium fr acquainting ptential fishfarmers with useful techniques. Plans include the rearing f all five lcal species f Pacific salmn plus steelhead trut, with the pssibility f rearing ther species f marine fish and invertebrates later. It was intended that the 1975 crp cnsist f abut equal numbers f chink, Oncrhynchus tshawytscha, ch, Q. kisutch and pink salmn, O. grbuscha, and that they be cultured frm the green egg stage t market size n the experimental fishfarm. Because f special circumstances, tw additinal small lts, ne f chink salmn and ne f steelhead trut, Salm gairdneri, were acquired as fingerlings and als reared. Sme sckeye salmn, Q. nerka, n which clleagues in the Fish Health Prgram were experimenting with vaccines, were als reared n the experimental fishfarm. MATERIALS AND METHODS EGGS fllws: Infrmatin n egg prcurement and hatching may be summarized as Apprx. Incubated Median Date number t eyed Place date Surce spawned f eggs stage at: hatched hatched Pink Adam R. Sept. 10/74 43,000 Rsewall Nanaim Nv. 25/74 Chink Smass R. Nv. 13/74 31,000 Nanaim Nanaim Feb. 20/75 Ch Big Qualicum Nv. 29/74 42,000 Nanaim Nanaim Jan R.

7 - 2 - SMOLTS Infrmatin n the chink salmn and steelhead trut acquired as smlts, as well as n the sckeye salmn reared frm the early smlt stage n the experimental farm, may be summarized as fllws: Apprx. Median Date number Date Place date int t Surce spawned hatched hatched fishpens fishpens Steelhead Thmpsn May 28 Technical unknwn Oct. 30/75 1,900 R. /74 Statin, Vancuver Chink Smass Nv. 15 Nanaim unknwn Aug. 6/75 1,600 R. /74 (nt fishfarm) Sckeye Fultn Oct. 8 Rsewall Dec. 10 Aug. 21/75 2,500 R. /74 /74 EARLY REARING Techniques were almst the same as reprted by Kennedy et al. (1976) fr the 1974 crp. Hwever, in 1975 the light timers were re-set weekly t give a daily "lights-n" time in the culture area apprximately equal t the average duratin f natural daylight fr that week. NET PEN REARING Techniques were als mainly as reprted fr the 1974 crp. Hwever, several minr mdificatins were made t netpens late in 1975 and early in Metal psts, 75 mm (3 in) in diameter were fixed t the flats, ne at each netpen crner. The tp crners f the netpens were thereafter tied t these psts, a mre efficient prcedure than the earlier ne f tying them t the bridges (Kennedy 1975). As a result the tp edges f all netpens were raised until they were almst a meter abve the water surface (cmpared with abut 30 cm earlier) t prevent fish frm jumping ut. Since mid-1975 a piece f 50 mm (2 in) mesh 1 netting is stretched ver each netpen and laced all arund t the tp edge. Als in 1975 the 13 mm (1/2 in) mesh netpens, when used, were hung inside 19 mm (3/4 in) mesh netpens. This arrangement made pssible the transfer f fish frm the smallest netpen t the next largest size with much less stress than in 1974 when the tw sizes f nets were in different places. lall mesh sizes are stretched measure.

8 - 3 - FEEDING Feeding was much as fr the 1974 crp. Lcally manufactured pellets, 4 mm (5/32 in) in diameter were usually fed t all fish large enugh t eat them, imprted OMP pellets f apprpriate smaller size being used fr smaller fish. Autmatic feeders were used t a greater extent than in 1975, particularly during the freshwater phase. DISEASE CONTROL The disease cntrl methds used in 1974 were als cntinued but with mre emphasis n vaccines fr cntrlling diseases in the marine envirnment. Almst all 1975 crp fish were vaccinated against furunculsis and against tw kinds f vibrisis, namely ne caused by Vibri angui11arum and ne caused by an as yet unnamed species f Vibri. The vaccines were prepared at Pacific Bilgical Statin frm lcal strains f the three kinds f bacteria that cause the abve three diseases. All three vaccines were mixed and administered simultaneusly. In the case f ch, chink and stee1head (nly abut half f the stee1head were vaccinated) the cmpsite vaccine was administered by needle t each fish individually. It was administered rally, mixed with the feed, t the pink salmn because they were t small fr the needle at the time f vaccinatin. A clleague expects t reprt separately and in detail n the administratin f vaccines t the sckeye. Cnventinal medicatin was used much less than in 1974 and when used was almst invariably su1phamerazine. FISH SIZE,FISH NUMBERS AND ENVIRONMENT Prcedures fr recrding data under these headings were as described in the reprt n the 1974 crp (Kennedy et a ). RESULTS CHINOOK Sme accident r errr in technique (just what is unclear) ccurr ed during the taking f chink spawn r shrtly after. As a result, 20% f the eggs died during the 1st day and heavy mrtality cntinued thereafter. Because the virus disease IHN was diagnsed amng the parent fish sn after the spawn was taken, it was cnsidered inadvisable t get a secnd lt f eggs frm the same surce and n ther was available. Als, because f the IHN diagnsis, the eggs were mved t a quarantine area as sn as they became eyed. Because the water supply t the quarantine area was nt heated, hatching was retarded. Abut 1,000 eggs (ut f 31,000) eventually hatched but all f the resulting fry died sn after.

9 - 4 - Meanwhile, anther lt f chi nk eggs had been taken frm the Smass River in cnnectin with a study f the IHN disease there. We eventually acquired apprximately 1,700 f the resulting fingerlings. Because they had been reared in unheated water, average weight when acquired was abut an rder f magnitude less than fr fish f the same age that had been reared n the experimental fishfarm. After being vaccinated by needle against bth kinds f vibrisis and against furunculsis, they were transferred t seapens n August 27, Instantaneus grwth rates2 in seapens were as indicated in Table 1. There was very mderate attritin unt il the fish had almst reached market size. Then, in the last 6 wk, heavy mrtality frm KD drastically reduced the number f fish. The survivrs were marketed n July 13, COHO As with the 1974 ch crp (Kennedy et al. 1976) smltificatin was a prblem. Apprximately half f the ch met expectatins by smltifying during the perid f increasing daylength (Le., befre June 21) and were transferred t seapens in early July 1975 (sme earlier). The rest were necessarily retained in freshwater tanks. In an attempt t induce the latter t smltify, the light timers were manipulated t simulate an accelerated summer, autumn and winter, all within the perid July-Octber. During that time apprximately ne-quarter f the ch still in fresh water smltified and were transferred t sea pens in late Octber (a few in Nvember). Thse still unsmltified were cntinued in freshwater in an area with natural lighting. By April 1976 all f the latter seemed t be smltified and were transferred t seapens, Because f the abve, the grwth f three separate grups f ch are fllwed in Table 2, namely: (1) all ch in fresh water at any given time until April 1976 then all ch transferred t seapens in April; (2) all ch transferred t seapens in May, June and July 1975; and (3) all ch transferred t seapens in Octber and Nvember. Grup 3 fish averaged just ver 50 g when transferred t seapens, three times the size f the unsmltified ch frm which they had recently been srted and abut half as large as thse that had smltified earlier. As time went n it was nted that abut 10% f the individuals in grup 3 were decidedly smaller than average. Parr marks culd usually be distinguished n these smaller fish, and mst f them were in cmparatively pr cnditin. It is nt clear whether they had "reverted" t the parr cnditin r whether they had been incrrectly classified as "smltified" in the first place. In any case they failed t grw as expected and their inclusin in the weight samples resulted in smaller values in clumn 5 f Table 2 than wuld have been the case had there been n "reverted parr." With "reverted parr" excluded, grup 3 ch were almst as large as grup 2 by February Instantaneus grwth rate means (very nearly) gain in weight during a given day as a percentage f ttal weight n that day.

10 - 5 - Majr changes frm ne mnth t the next in the number f fish recrded in clumns 1 and 2 f Table 2 are assigned causes as fllws: Clumn March-Apri1l75 1 Cause Lsses frm a gill infectin. June-Aug./75 1 and 2 Transfer t sea pens where lsses frm tter predatin were heavy. Oct.-Nv./75 1 and 2 Transfer t seapens. April-June/76 1 Lsses frm grebe predatin and escapement. The rearing f ch that had been transferred t seapens in 1975 was terminated February 13, 1976 when substantial numbers had reached market size. Rearing f the few survivrs f thse transferred in 1976 was terminated n July 6, PINKS The pink salmn were transferred frm fresh water t sea water in tanks in January 1975 when they averaged abut 0.25 g. At an early stage an abnrmal gill cnditin had been diagnsed as the result f vitamin deficiency (pantthenic acid and tcphera1) and treated by adding mre vitamins t the feed. The decline in estimated numbers f ch shwn in Table 3 fr February and March 1975 is attributed mainly t mrtality frm this cause. They were held in pumped sea water until transferred t seapens in April and May. The twine in ne f the tw seapens int which pinks were initially intrduced had been stiffened by an anti-fuling preparatin (see belw). Mst f the fish in the treated netpen sn had injured snuts. As sn as extensive damage was nted the fish were mved t a nn-treated seapen where the damaged snuts gradually healed. An utbreak f vibrisis (frm Vibri angui11arum) was cntrlled by treatment with su1phamerazine an furxne. It was immediately fllwed by an utbreak f piscine erythrcytic necrsis (PEN) that caused heavy mrtality. Simultaneus with bth disease utbreaks was heavy tter predatin. The dramatic decline in numbers f pink salmn frm May t July shwn in Table 3 is the cmbined result f vibrisis, PEN and tter predatin. Rearing in seapens cntinued until March 12, 1976 when all were slaughtered fr market. KD had becme an increasing cause f mrtality twards the end f the rearing perid but when all slaughtered fish were examined the number discarded because f bvius symptms f KD was negligible. Instantaneus grwth rates are given in Table 3. They apprximate the expected pattern, i.e., an early increase t a high grwth rate, fllwed by a steady decline in rate as size increased, the whle being mdified by

11

12 - 7 - Instantaneus grwth rate was abut 2% until late September, then virtually nil until mid-nvember, cincident with reduced feeding during a blm f Chaetcers, a sckeye-killing plankter. Instantaneus grwth rate was abut 1.4% Nvember-January. Because it was undesirable t fllw usual practice in sampling the fish, grwth rates are unre liable after January MORTALITIES AND OTHER ATTRITION Table 4 presents data n mrtality and ther attritin fr the 1975 crp f ch~ pink and chink salmn. Disease remained a serius prblem, althugh less serius than fr the 1974 crp, als the relative imprtance f specific diseases changed nticeably. Amng ch, pink and chink salmn (and steelhead trut) n mrtalities were attributed t either furunculsis r t the kind f vibrisis caused by the unnamed Vibri, and nly limited mrtalities amng pinks and steelheads frm vibrisis caused by y. anguillarum. The dramatic change frm heavy mrtality frm these three diseases amng the 1974 crp seems related t the fact that the 1975 crp f ches, pinks and chinks and half f the steelheads had been vaccinated against all three diseases. Vibrisis amng pinks seems related t: (1) use f ral vaccine in their case as ppsed t vaccinatin by needle fr the thers; and (2) the stress f incipient PEN disease. The utbreak amng steelheads is regarded as the cnsequence f vaccinating nly half f them. Mrtality was relatively lw when these utbreaks did ccur, indicating effective cntrl measures by antibitics. The disease PEN amng pink salmn is discussed belw. Chaetcers was nly a minr cause f mrtality amng the 1975 crp. The nly cuntermeasure t Chaetcers was t avid disturbing the fish, including a reductin in feeding, during Chaetcers blms. Starting abut May 1975 Kidney disease, r KD, became chrnic at a lw level amng all stcks f the 1975 crp f ch, whether in fresh water r in seapens. Mrtalities frm KD increased as the fish apprached market size but never reached a high level. KD was the main cause f death in pink salmn after December 1975 and killed many sckeye after that date. After 9 m f ntably gd survival, tw-thirds f the chinks died frm KD during the last 6 wk befre reaching market size. Predatin by tters, Lutra canadensis, was again a serius cause f attritin, invlving ch and pink salmn that had been in seapens fr a cmparatively shrt time. A number f ways f cping with tter predatin were tried befre a successful me~hd was fund. The methd nw used is t spread ver the tp f each seapen a piece f netting large enugh t cver the seapen and verlap abut 3 ft beynd it all arund. This cver is then laced t the tp lines f the seapen all arund. The cver is a nuisance when bserving fish r manipulating the seapen t cncentrate them, but anything less is nw regarded as inadequate prtectin against tters. Starting August 11, 1975 cvers have been laced n all seapens while in use. Since that date there des nt seem t have been any tter predatin. Otters have, hwever, been in the vicinity; e.g., tter faeces have been fund ccasinally n the flats that supprt the netpen (but with decreasing frequency) and nce an tter was seen swimming under a netpen.

13 - 8 - Fr Table 4 tter predatin was equated with that part f the difference between tw successive estimates f fish numbers that culd n t be accunted fr therwise during a pe rid when tters were knwn t frequent the vicinity, smetimes even being seen inside seapens. Sme r all f the fish recrded as taken by tter culd have been already dead frm disease, r s sick that they wuld have died frm disease had there been n tter. Fr these reasns the recrded attritin frm tters is prbably t high. On the ther hand, by preying n pink salmn with PEN, thereby rem v~ng surces f infectin (a live a nd dead), the tters may have reduced mrtality frm disease. Apprximately 7,500 ch disa ppear ed mysteriusly frm a seapen between April 13 and May 12, Fur independent inspectins f the net made subsequently revealed that the seapen wa s intact, except fr a ne tw-bar and ne ne-bar hle fund n the f urth inspectin and perhaps made by the cnsiderable handling asscia ted with earlier inspectins. The tp had been laced n and the lacings were undisturbed precluding the pssibility f predatin by tter, mink r airbrne birds. A few fish prbably died and decmpsed withut being cunted but had the number been significant the cunt f mrtalities recvered during regular inspectins wuld have been much higher than it was. Sme fish were bserved t wriggle thrugh the mesh, immediately after they were put in the seapen and lss thrugh the mesh was prbably substantial. Hwever, we als attribute part f the lss t predatin by western grebes, Aechmphrus ccidentalis. The ch in questin were thse that had been slw t smltify and were nly mved t a seapen n April 13, Sn after, western grebes were seen swimming and diving in the immediate vicinity f that particular seapen (and n ther) in increasing numbers. Fr abut 10 days starting in late April, grebes (nt necessarily the same grebes) were there cntinually, and a cncerted effrt t drive them ff had n effect. Simultaneusly, increasing numbers f living and dead ch in the seapens had wunds that bviusly had been inflicted by grebe beaks. Apprximately half f the survivrs by May 12 had been s wunded and when the sea pen was remved fr examinatin we fund the remains f a western grebe that had died afters its beak became entangled with the netting that frmed the bttm f the seapen. We pstulate that a grebe wuld seize a fish attempting t wriggle thrugh the mesh r wuld even reach thrugh a mesh f the netting (as the dead bird presumably was ding) seize a fish (perhaps wunded r killed earlier) and pull it thrugh the mesh. Since the size distributin f ch befre and after indicate that grebes tk all sizes f ch at randm, they must have pulled ch as big as 50 g thrugh the 25 mm (1 in) mesh. The fact that in gillnet fisheries fr certain species the fishermen rutinely pull captured fish thrugh meshes much t small fr them t swim thrugh makes the abve credible. Failure t smltify, as a cause f attritin amng ch, is prbably underestimated in Table 4. Ch that failed t smltify (this includes thse that "reverted t parr") survived in seapens fr as much as 6 m, perhaps mre, while their health prgressively deterirated as indicated by failure t grw and increasingly abnrmal external appearance. Althugh they eventually

14 - 9 - succumbed t disease, it wuld seem that the real cause f death was failure t smltify. Als amng the ch classified as "reached target size" in Table 4, there were mderate numbers f unsmltified individuals that either died r were discarded after the terminal date. Slwness t smltify was bviusly invlved in the heavy predatin by grebes and in the simultaneus escapement thrugh the meshes, and it is quite likely that many f the fish invlved were "reverted parr." PISCINE ERYTHROCYTIC NECROSIS OR PEN As the name suggests, the disease is characterized by destructin ~ red bld cells. A fish is diagnsed as having PEN when inclusins f a specific type are seen during micrscpic examinatin f sme f its red bld cells (ne inclusin per cell). The appearance f such an inclusin is the prelude t death f that cell. Fish with PEN have cmparatively lw haematcrits, and red bld ce 11 cunts becme very lw just' befre the individual fish dies. There was sme PEN in the 1974 crp f chum salmn (Kennedy et al. 1976), apparently the first time that PEN had been diagnsed in salmn anywhere. It was diagnsed amng the 1975 crp f pink salmn n June 19 but it did nt appear amng any ther fish f the 1975 crp. On June 25, 1975 at the height f the PEN epidemic in pinks, 85% f a representative sample had PEN, and their average haematcrit was 21. Subsequent examinatin f representative samples shwed a gradual decline t 20% infected August 5, 12% September 25 and 0 December 22. Als, as time went n the prprtin f red bld cells with inclusins declined markedly, even amng infected fish, indicating that thse still infected were n lnger as seriusly infected. Haematcrits returned t the "nrmal" (40-50) level by August 5. At the peak f the epidemic PEN killed mre than 1,000 fish per day. Overall it killed abut 7,000 fish, mstly during the first 2 wk. Frm June 19 t July 15 we added beef liver t the usual pelleted feed, ne part liver t nine parts pellets by weight with additinal water as a binder. Adding liver was a desperate attempt t treat fr PEN, n recgnized treatment being available. Althugh feeding liver cincided with a dramatic decline in mrtalities frm PEN and with recvery frm the disease, it is nt clear whether the "treatment" had any effect r whether the disease wuld have abated just as quickly withut it. A crude experiment, devised at shrt ntice, was cnducted. A representative sample f pink salmn taken n June 25 was divided int three lts. One lt was fed the regular diet, ne the regular diet plus liver and ne

15 liver nly. Results were as fllws (it was nted that the general cnditin f the "liver nly" fish gradually deterirated presumably because liver alne is nt an adequate diet): Haematcrits Number pellets pellets liver examined nly and liver nly June July (5 each) Aug (5 each) The data suggest that liver may supply sme dietary factr needed t cntrl PEN. Hwever, because f makeshift experimental cnditins and small numbers, these results need cnfirmatin. In any case, the suggestin that PEN may be assciated with sme dietary deficiency is well wrth further study. ANTI-FOULING TREATME~ The immersed part f a seapen sn becmes cated with sessile marine rganisms which bth grw and entangle planktn and debris resulting in an ever increasing buildup f "marine fuling" n the netting. We usually deal with the prblem by peridically replacing fuled nets by clean nes, the fuled nets being cleaned and dried befre re-use. Hwever, we have als been interested in the idea f preventing, r at least inhibiting, marine fuling by chemical means. Several chemicals were cnsidered and rejected either because f reprts that they were ineffective, r because the risk t fish seemed t high. In the end nly ne suggested chemical seemed wrth testing, namely a German prduct knwn as, Wiedx V.F. 6500l/grun. We treated tw brand new nets (seapens) with Wiedx V.F accrding t the directins given. The web f the treated seapens became ntably less flexible and ntably harder surfaced as a result f the treatment. When pink salmn were held in ne f these seapens, a large prprtin f them sn had seriusly damaged snuts. Pink salmn in an identical neighbring seapen that had nt been treated shwed n snut damage. When the pink salmn in the treated netpen were mved t an untreated seapen n further snut damage ccurred and the already damaged snuts gradually healed.

16 We nw regard Wiedx V. F as an unsuitable anti-fuling agent fr fishfarm seapens because it alters the physical characteristics f netting in a way that is detrimental t captive fish. It des slw the rate at which marine fuling builds up, but it des nt prevent it. One authr (W.A.K.) has bserved that many fishfarmers in Japan use sea pens made f galvanized wire r plastic-cated wire, because, they claim, buildup f marine fuling is slwer n, and it is mre easily remved frm, these materials than cnventinal netting. Dr. D. B. Quayle (persnal cmmunicatin) attributes the anti-fuling actin f galvanized and plasticcated wire t the difficulties that sessile rganisms have in becming established and remaining established n smth surfaces. It, therefre, seems likely that the anti-fuling actin f Wiedx V.F (such as it is) cnsists nly f changing the physical characteristics f the twine f which the seapen is made, making it hard and relatively smth. In an effrt t remve Wiedx V.F frm ne f the treated seapens it was saked in sea water fr mre than a mnth withut any lss f the chemical, prviding further evidence that any anti-fuling actin is physical rather than chemical. MARKETING The marketable part f the 1974 and 1975 crps f salmn were sld during January-July The number f 1975 crp fish that Table 4 indicates reached target size and the numbers f 1974 crp fish in a crrespnding table (Kennedy et al. 1976) is cnsiderably greater than the number actually sld because: 1. There was heavy mrtality, mainly frm KD, between the time that detailed recrd keeping ceased when a substantial number had reached market size and the time that the last f a given lt were sld. 2. Undersize fish were discarded at the time f sale, particularly amng ch where many had failed t smltify r had reverted t the parr cnditin. 3. Several hundred punds f fish were used fr purpses such as free samples t ptential buyers that were unacquainted with the prduct. Except fr pink salmn, all were sld in the rund, unpackaged, F.O.B. Nanaim r Victria, B.C. Rughly ne-quarter f the pinks were sld fresh, dressed head-n, and packaged, F.O.B. Victria airprt, the rest as frzen, dressed head-n and packaged, F.O.B. Nanaim. Ttal sales, cnverted t rund weight where apprpriate, were as fllws: sckeye ch pink chink Ttal 1,371 lb 2,219 lb 2,275 lb 207 lb 6,072 lb

17 Gr ss value f all sales was $4, The average price was therefre ' 77. 5t per pund f rund weight. Actually the price n individual sales var ied f r m50t t $1.00 per pund f rund weight. The fur species were equally acceptable (as chum salmn wuld als be) althugh ne buyer indicated a preference fr chinks because f his experience with keeping qualities f cmmercially caught salmn. Species was nt a factr in the variatin in price per pund. Because f special circumstances related t ur inexperience, t the small quantity available fr sale, t gvernment regulatins pertaining t the dispsal f crwn assets and t pressing needs fr the netpens that the fish ccupied, the average price per pund received was lwer than t hat which we understand lcal fishfarmers have received recently, namely abut 95 t per pund fr unpackaged fish in the rund F.O.B. the seapens. FISH FLESH COWR As nted in an earlier reprt (Kennedy et al. 1975) the flesh f pen-r eared salmn reared t market size (300 g) n a typical pellet diet is white, and the additin f 15% shrimp mea l t the pellet ingredients changes the clr nly marginally. Carphyl13, a cartenid used in pultry feeds fr intensifying the clr f egg ylks, was used in an attempt t increase flesh clr in sme f the 1975 crp salmn sld in Carphyll was mixed with ur usual feed during the pelleting prcess in the rati 1 kg f carphyll t 900 kg f feed. Carphyll-enriched feed was fed t ch and chink salmn fr 32 days and 57 days, respectively. In each case the flesh became satisfactrily clred. The clr was less intense than in mst adult salmn and was mre yellwish, but seemed t meet bjectins ften raised t the lack f clr in the flesh f pan-size pen-reared salmn. VITAMIN C FOR KD In an earlier reprt (Kennedy et al. 1975) the pssibility f cntrlling KD by massive dses f Vitamin C was raised. Because f serius illness Dr. A. T. Wd, University f Victria has nt cntinued investigatin f this pssibility. We fed 10 times the usual amunt f Vitamin C t 1,000 (initially) ch in a seapen fr 2t m. It seemed t give n prtectin against KD. Investigatins by Dr. T. Evelyn, Fish Health Prgram, Pacific Bilgical Statin, (persnal cmmunicatin) als indicate that massive dses f Vitamin C ffer n prtectin against KD t ch salmn. DISCUSSION Althugh ur experience with steelhead trut has been limited, it has sufficed t indicate that they are prbably the least suitable f the 3A registered trade name. n request. Name and address f the manufacturer supplied

18 six salmnid species being cnsidered fr cmmercial rearing in seapens. The prlnged freshwater perid required, the care required t adapt them frm fresh water t sea water, and their medicre grwth rate in sea water, are all unfavrable characteristics. Experience with the 1975 crp f salmn in general has greatly increased ur cnfidence in vaccines as a means f cntrlling furunculsis and the tw kinds f vibrisis that have caused heavy mrtality in the past. Althugh ral vaccine is generally cnsidered t be less effective than vaccine by needle, we cnsider even ral vaccines a tremendus imprvement ver n vaccine. In spite f these encuraging results, it seems desirable t have antibitics n hand fr immediate use in case vaccines against furunculsis r vibrisis are nt cmpletely effective. Sulphamerazine seems t be a particularly effective antibitic fr these diseases, but ne r mre alternative antibitics (e.g., terramycin, sulphamethazine r furx) shuld als be readily available. With furunculsis and the tw kinds f vibrisis cntrlled, KD has becme the mst serius disease. It can be particularly serius t a cmmercial fishfarmer because it typically nly becmes manifest just befre the fish reach market size. As an extreme example, tw-thirds f the 1975 crp f chink died frm KD just befre reaching market size after excellent previus survival. KD cannt be cntrlled by any knwn antibitics and massive dses f Vitamin C als appear ineffective. Mst f the 1976 crp f ch have been vaccinated against KD and infrmatin n the effectiveness f KD vaccine will prbably be reprted in PEN remains a ptential appeared in pink and chum salmn. althugh the feeding f liver may results frm a dietary deficiency amng the pssible deficiencies. hazard. Hwever, it has s far nly There is n recgnized treatment fr PEN be beneficial. The pssibility that PEN shuld be investigated, irn being It appears that tter (and incidentally mink and airbrne birds) predatin can be prevented by putting suitable tps n seapens. It is cnsidered imprtant that a dg als patrl the area, a large aggressive dg is required. Western grebes caused cnsiderable mrtality amng ne lt f ch by spearing them with their beaks thrugh the mesh. Althugh ther species f diving birds had previusly pecked seapen fish n rare ccasins, western grebes pierced a much greater prprtin f the fish in questin, and, unlike ther diving birds, apparently managed t pull fish (whether alive r dead is nt clear) thrugh the mesh. Predatin by western grebes prbably resulted frm unusual circumstances, nt likely t recur. On the particular ccasin ch were mved frm freshwater tanks t seapens at an unusual time and just when western grebes were migrating thrugh the area. When ch are first mved t seapens a large prprtin f them repeatedly swim against sides and bttm, giving every appearance f purpseful attempts t escape. Newly intrduced ch, by being near the sides and bttm, wuld be much mre vulnerable t grebes than they wuld

19 be after a few weeks when they tend t distribute themselves fairly evenly thrughut the vlume f a seapen. The relatively small size f the newly intrduced fish was als a f a ctr; l a r ge fish culd nt have been retrieved thrugh the mesh. Als sme ch were seen t wriggle thrugh the mesh; while ding s they wuld have been particularly easy prey fr grebes. The fact that sme ch were seen t wriggle thrugh the mesh indicates that we need t review, a nd in sme cases revise upward, minimum sizes at which salmn are intrduced t seapens f varius mesh size. We attained an bjective by demnstrat i ng that salmn can be reared t market size (300 g) in seapens a nd that they can be sld t fish dealers. It became bvius during the marke t i ng prcess that the kind f dealers that buy relatively small and erratic quantities f fish such as we prduce n the experimental fishfarm are nt the same kind f dealers that culd handle the larger quantities f fish t hat a typical cmmercial peratin wuld prduce. It appears that the typical buyer fr larger quantities f pan-size salmnids expects fish f unifr m size, delivered n a sustained basis ver a leng~perid f time, dressed and suitably packed. At the present state f the art we culd prbably nly meet these requirements by accurately grading the fish just befre marketing them, by dressing them and freezing them s that they culd be released frm cld strage at a steady rate t maintain a steady supply ver many mnths. We culd prbably nt justify the purchase f the very expensive mechanical srter needed, nr find it practical t have ur wn fish prcessing and freezing facilities, nr (as an alternative t wning) find it ecnmical t cntract fr prcessing and freezing nr divert peple t perate the marketing system required. Therefre, it seems likely that the experimental fishfarm's utlet fr penreared salmn must necessarily cntinue t be small peratrs such as lcal fish stres, unless the decisin is t virtually give the fish away. Under these circumstances we can nly t a limited extent simulate marketing n a full-scale fishfarm. One pint n which mst fish buyers agreed was that salmn flesh shuld be clred rather than white; a cmmn pinin was that clr wuld increase selling price by at least 25 per pund (althugh we nly gt l5 mre fr clred fish). We have demnstrated with 1975 crp fish that pen-reared pan-size salmn flesh can be clred satisfactrily by adding carphyll t the diet. The characteristic flesh clr f typical cmmercially caught salmn results frm ingestin f the cartenids fund in the tissues f their prey (especially in crustacea). There is essentially n difference between the tw, in each case fish flesh is clred because f cartenids in the feed. Carphyll r its equivalent, is used in at least ne large cmmercial peratin in Britain t clr the flesh f seapen-reared salmnids and its use fr that purpse seems legal in Canada althugh it is said t be illegal in the U.S.A. Apparently,the regulatins that make its use illegal in the U.S.A. als wuld make it illegal t feed fishfarm salmn there n the very crustacea that wild salmn eat if the purpse was t clr the flesh, althugh it seems t be legal t feed these r ther crustacea t fishfarm salmn if the purpse is t nurish them.

20 CONCLUSIONS 1. We have demnstrated that sckeye, ch, chink, and pink salmn, reared in captivity t pan-size, can be sld fr human fd. 2. Steelhead trut seem less suitable fr cmmercial seapenrearing than any f the five lcal species f Pacific salmn. 3. The use f vaccines has dramatically decreased lsses frm furunculsis and frm the tw kinds f vibrisis recgnized lcally. Antibitics are a useful ancillary t vaccines. 4. KD has emerged as a very serius disease fr which n treatment is available althugh a vaccine is under test. 5. PEN is nw recgnized as a disease that may cause heavy mrtality in pen-reared pink and chum salmn. 6. There has been n prgress twards cping with Chaetcers as a killer f pen-reared sckeye salmn. 7. Suitable tps fr seapens plus a suitable dg seem adequate means f preventing tter predatin; earlier lsses by the 10,000's annually have been reduced t 0 fr the past year. 8. We have been unable t find a satisfactry chemical fr inhibiting marine fuling n seapens. 9. Carphyl1, the registered trade name f a cartenid preparatin, when added t the regular diet, clrs the flesh f pan-size pen-reared salmn satisfactrily. 10. The pssibility that PEN is caused by sme deficiency in the diet, perhaps irn, shuld be investigated. BIBLIOGRAPHY Kennedy, W. A., C. T. Shp, and W. Griffien Preliminary experiments in rearing Pacific salmn (1973 parr) in pens in the sea. Fish. Mar. SerV Res. Dev. Tech. Rep. 541: 17 p. Kennedy, W. A An experimental fishfarm fr salmn at the Pacific Bilgical Statin. Fish. Mar. Serv Res. Dev. Tech. Rep. 543: 33 p. Kennedy, W. A., C. T. Shp, W. Griffien, and A. Slmie The 1974 crp f salmn reared n the Pacific Bilgical Statin experimental fishfarm. Fish. Mar. Serv Res. Dev. Tech. Rep. 612: 19 p. Ryan, P A raft fr five mariculture nets. Fish Mar. Serv Res. Dev. Tech. Rep. 544: 9p.

21 Table 1. Attritin and grwth f chink salmn f the 1975 crp reared n the experimental fishfarm, Pacific Bilgical Statin. Average Estimated water number f Instantaneus temperature fish at grwth rate during first f during mnth mnth Mnth mnth % C Remarks Started Aug. 6 with an estima ted 1,671 fingerlings. Sept. 1, All t seapen Sept. 10. Oct. 1, Nv. 1, Dec./75 1, Jan./76 1, Feb. 1, Mar. 1, Apr. 1, May 1, June 1, July 606 Terminated July 13, final estimate 360 fish.

22 Table 2. Attritin and grwth f ch salmn f the 1975 crp reared n the experimental fishfarm, Pacific Bilgical Statin. Clumn Estimated number f Instantaneus grwth rate Average water fish at first f mnth during mnth temperature - C Fish in fresh water Clumn 2 Clumn 2 Applicable until Apr./76 Fish t All f fish t fish t Applicable t Clumns Remarks then t sea pens Clumn 1 seapens seapens t Clumn 4 and 5 (numbers f fish Mnth seapens in 1975 fish May-July Oct.-Nv. 3 fish fish are estimate&l Started Feb. 19 with an estimated 35,967 fry. March/75 33, Apr. 30, May 30, fish t seapens. June 30, ,438 fish t seapens. July 26,200 1, ,526 fish t seapens. Aug. 13,038 4, Sept. 12,926 4, Oct. 12,801 4, ,555 fish t seapens. Nv. 9,167 7, fish t seapens. Dec./75 9,161 7, Jan./76 8,996 6, ~ Feb. 8,934 6, Rearing f Clumn 2 fish terminated. Feb. 13-6,108 fish. t--' -...J

23 Table 2 (cnt'd) Clumn Estimated number f fish at first f mnth Instantaneus grwth rate during mnth Average water temperature - C Mnth Fish in fresh water until Apr./76 Fish t then t seapens seapens in 1975 Clumn 2 Clumn 2 All f fish t fish t Clumn 1 seapens seapens fish May-July Oct.-Nv. Applicable Applicable t Clumns t Clumn 4 and 5 3 fish fish Remarks (numbers f fish are estimates) March Apr. May June July 8,820 8,185 4, ,013 fish t seapens Apr. 13. Terminated July 6. I-' 00

24 Table 3. Attritin and grwth f pink salmn f the 1975 crp reared at the experimental fishfarm, Pacific Bilgical Statin. Estimated number f Instantaneus Average water fish at grwth rate temp. during Remarks first f during mnth mnth (numbers f fish Mnth mnth % C are estimates) Feb. 34, March 29, Started Jan. 7 with an estimated 34,704 fry. Apr. 28, Apr ,336 t seapens. May 26, May 27-7,182 t seapens. June 16, July 9, Aug. 6, Sept. 6, Oct. 6, Nv. 5, Dec. /75 5, Jan. /76 5, Feb. 5, March 5,113 Terminated March 12 - final estimate 4,932 fish.

25 Table 4. Causes f mrtality and ther attritin as assigned subjectively; expressed as percentages f the number f fry at the stage when feeding became cnsistent in the case f ch and pink and as a percentage f the number f smlts acquired in the case f chink. A 11+" signifies less than 0.5%. Cause f mrtality r attritin Ch Pink Chink Freshwater attritin - - Diseases - Water failure - Escaped - Other Diseases in seapens - Vibrisis frm V. anguillarum - Vibrisis frm V. sp. - Furunculsis - KD - PEN - Chaetcers N Failure t smltify + Predatrs Escaped 10 Miscellaneus mrtalities in seapens Samples and diversin t experiment Reached target size (usually market size) Estimated riginal number f fish 35,967 34,704 1,671