W.Craig Clarke

Evaluation of Tower and Candle rapeseed (canola) meal and Bronowski rapeseed protein concentrate as protein supplements in practical dry diets for juvenile chinook salmon (Oncorhynchus tshawytscha)

Abstract A laboratory study and a pilot-scale hatchery experiment were carried out to determine the acceptability of rapeseed products as protein supplements in diets for chinook salmon. Replacement of 10 and 13% of the protein in a modified Abernathy dry diet with protein from Tower or Candle rapeseed meal or Bronowski rapeseed protein concentrate did not alter growth rate, food or protein utilization, body composition, thyroid or pituitary cytology, osmoregulatory capacity, health or mortality of chinook salmon. However, growth rate and food (protein) utilization were reduced when 25% of protein was replaced by rapeseed meal, but not when replaced by Bronowski rapeseed protein concentrate. Condition factors of chinook fed rapeseed products at the intermediate or highest levels were often significantly elevated. Hatchery performance of chinook salmon fed a dry diet where 13% of protein was provided from Tower meal was similar to that when Oregon moist pellets were fed except for a compensatory increase in thyroid activity in the former fish. It is concluded that rapeseed products of the canola type are good protein supplements for chinook salmon and can comprise 13 to 16% of dietary protein (16 to 20% of dietary dry matter).

Effect of artificial photoperiod cycles, temperature, and salinity on growth and smolting in underyearling coho (Oncorhynchus kisutch), chinook (O. Tshawytscha), and sockeye (O. nerka) salmon

Abstract Of the three environmental factors investigated, temperature had the stongest influence on growth of sockeye, coho, and fall chinook fry (starting weights 0.7, 0.7, and 1.2g, respectively). Growth of coho was significantly greater under a changing photoperiod than under a constant 12h photoperiod, whereas the chinook fry showed no consistent growth response to the photoperiod treatments. Hypo-osmoregulatory ability of juvenile coho in sea water was influenced by photoperiod, but none of the photoperiod treatments produced optimum osmoregulatory performance. Salinities up to 20‰ had little effect on growth rate in coho, sockeye, or chinook, but did prevent loss of hypo-osmoregulatory ability in the latter species at 15°C. Transfer to 29‰ during the second half of the 12-week experiment resulted in slower growth of sockeye and chinook smolts.

Effect of initial daylength on growth, seawater adaptability and plasma growth hormone levels in underyearling coho, chinook, and chum salmon

Abstract Chum ( Oncorhynchus keta ), coho ( O. kisutch ), ocean and stream-type chinook ( O. tshawytscha ) salmon fry were reared from first feeding under constant 9.5 h or 14.5 h photoperiod for 2 months and then under simulated natural photoperiod for 4 months. The coho and stream-type chinook grew more rapidly and more uniformly both in fresh and in salt water after short than after long day treatment. In contrast, the chum and ocean-type chinook salmon grew well and adapted readily to sea water after either treatment. Plasma growth hormone levels in June or in August were not significantly different between photoperiod treatments in any of the species. It is concluded that juvenile coho and stream-type chinook require a period of exposure to short day photoperiod from first feeding in order to develop uniformly as zero-age smolts. This experiment showed that zero-age coho or stream-type chinook smolts can be produced using a 2-month constant short day photoperiod under simple lighting systems.

Evaluation of the seawater challenge test as an index of marine survival

Abstract This paper reviews the studies undertaken to determine the relationship between hypoosmoregulatory performance in the 24-h seawater challenge test and marine survival of hatchery-reared coho salmon and steelhead trout juveniles. The results of sampling various salmonids in southwestern British Columbia are discussed in terms of potential utility of the challenge test in relation to increasing the efficiency of hatchery production. Although some individuals of all salmonid species tested exhibit a similar high level of hypoosmoregulatory performance in the challenge test, the size at which this development appears varies widely among species. Sampling of juveniles from structured release experiments in production hatcheries has revealed temporal and size-related differences in the pattern of development. Once the information on rate of survival of these release groups is available, it is anticipated that particular levels of performance can be interpreted in relation to species and locale.

Impact of a controlled release formulation of recombinant bovine growth hormone upon growth and seawater adaptation in coho (Oncorhynchus kisutch) and chinook (Oncorhynchus tshawytscha) salmon

Abstract Experiments were undertaken to evaluate a sustained release recombinant bovine growth hormone (rbGH) formulation (Posilac®) in salmon. The investigation was divided into two parts. The first series of studies was used to establish optimal dosages and clearance rates for the exogenous protein in size-selected coho salmon, and to examine the effect of rbGH treatment upon smoltification. The second series of studies attempted to mimic the production setting, where chinook salmon were randomly selected from a stock of animals, and taken through smoltification to grow-out. In the first experiment, coho salmon were provided with a single injection of one of three doses (420, 1260, 4200 μg/g body weight equivalent) of the rbGH preparation (n ≥30/group), or were injected with a saline solution containing the high dose equivalent of rbGH. Controls were treated with BSA, given one of three (10, 30 or 100 μl) placebo carrier preparations without rbGH, or left untreated. Animals receiving rbGH by sustained-release expressed highly significant (P

Cloning and functional pharmacology of two corticotropin-releasing factor receptors from a teleost fish

Although it is well established that fish possess corticotropin-releasing factor (CRF) and a CRF-like peptide, urotensin I, comparatively little is known about the pharmacology of their cognate receptors. Here we report the isolation and functional expression of two complementary DNAs (cDNAs), from the chum salmon Oncorhynchus keta, which encode orthologues of the mammalian and amphibian CRF type 1 (CRF(1)) and type 2 (CRF(2)) receptors. Radioligand competition binding experiments have revealed that the salmon CRF(1) and CRF(2) receptors bind urotensin I with approximately 8-fold higher affinity than rat/human CRF. These two peptides together with two related CRF-like peptides, namely, sauvagine and urocortin, were also tested in cAMP assays; for cells expressing the salmon CRF(1) receptor, EC(50) values for the stimulation of cAMP production were between 4.5+/-1.8 and 15.3+/-3.1 nM. For the salmon CRF(2) receptor, the corresponding values were: rat/human CRF, 9.4+/-0.4 nM; urotensin I, 21.2+/-2.1 nM; sauvagine, 0.7+/-0.1 nM; and urocortin, 2.2+/-0.7 nM. We have also functionally coupled the O. keta CRF(1) receptor, in Xenopus laevis oocytes, to the endogenous Ca(2+)-activated chloride conductance by co-expression with the G-protein alpha subunit, G(alpha16). The EC(50) value for channel activation by rat/human CRF (11.2+/-2.6 nM) agrees well with that obtained in cAMP assays (15.3+/-3.1 nM). We conclude that although sauvagine is 13- and 30-fold more potent than rat/human CRF and urotensin I, respectively, in activating the salmon CRF(2) receptor, neither receptor appears able to discriminate between the native ligands CRF and urotensin I.

Growth and development of seawater adaptability by juvenile fall chinook salmon (Oncorhynchus tshawytscha) in relation to temperature

Abstract Fall chinook salmon ( Oncorhynchus tshawytscha ) fry were reared in fresh water and transferred to sea water at intervals in order to determine the optimum conditions for entry into sea water. The three factors in the experiment were temperature in fresh water (7 to 17°C), temperature in sea water (9.5 to 14.5°C) and time of transfer to sea water (April to June). Fry of 1.50 g and larger could survive and grow in sea water. There was a considerable delayed mortality in sea water associated with scale loss in fish which were reared in warm water. The optimum for regulation of plasma sodium concentrations occurred with transfer of 5.6-g fish from 13.8°C fresh water to 10.2°C sea water on 18 May. Maximal growth in sea water relative to that in fresh water occurred with transfer of 6-g fish from 9.7°C fresh water to 14.1°C sea water on 11 June.

Inheritance of smolting phenotypes in backcrosses of hybrid stream-type × ocean-type chinook salmon (Oncorhynchus tshawytscha)

Chinook salmon (Oncorhynchus tshawytscha) are ecologically and geographically differentiated into two life history types: “ocean-type,” which enter estuaries as fry or fingerlings in the first year of life and rear there for up to 6 wk before migrating to sea, and “stream-type,” which migrate seaward as smolts after one or more years in fresh water and are only transient residents in the outer portion of estuaries. Following exposure to a long-day priming photoperiod for 2 mo from the time of first feeding, progeny of stream-type chinook salmon undergo a reduction in growth during summer and remain as parr, whereas progeny of ocean-type chinook salmon and hybrids continue to grow during the summer and develop into underyearling smolts. Male purebred and hybrid F1 progeny of ocean-type and stream-type chinook salmon were backcrossed to females of both parental populations to examine the segregation of photoperiod-independent (smolt) and photoperiod-dependent (parr) phenotypes among progeny. Results of the backcrosses of the hybrid F1 males depended on female type. The backcross to ocean-type females produced progeny that were predominantly smolts, whereas progeny from the backcross to stream-type females segregated into approximately equal numbers of smolts and parr. These results are consistent with Mendelian inheritance of a single major gene with two alleles: a dominant allele for the photoperiod-independent phenotype of ocean-type chinook salmon and a recessive allele for the photoperiod-dependent phenotype of stream-type chinook salmon.

Effects of a dietary betaine/amino acid additive on growth and seawater adaptation in yearling chinook salmon

Abstract The effect of FinnStim, a betaine/amino acid mixture, on growth and seawater adaptation was studied in yearling chinook salmon Oncorhynchus tshawytscha . The fish were marked with PIT tags and divided into two groups. One group was fed a diet with 1% FinnStim added and the other was fed a control diet with 1% α-cellulose. The diets were fed for 6 weeks in fresh water at a level of 1% body weight per day and for 8 weeks in seawater netpens at 3% body weight per day. Seawater challenge tests were conducted three times during the freshwater phase of the experiment. Growth and mortality in fresh water did not differ significantly between treatments. Seawater challenge tests at days 5, 47 and 70 of freshwater rearing revealed no significant difference in plasma sodium concentration between groups. During the seawater phase of the experiment, the group receiving FinnStim had a significantly higher growth rate and a significantly lower concentration of plasma sodium at the end of the study. The improved growth performance in the group receiving FinnStim was due to a reduction in the number of salmon growing poorly.

Effect of growth on early sexual maturation in stream-type chinook salmon (Oncorhynchus tshawytscha)

Abstract The proportion of sexually mature yearling chinook salmon varied from 23–80% of the males, being elevated in larger, faster growing fish. It was 2.5 times higher in fish fed to satiation compared with those kept on a restricted ration from November through June. In chinook fed to satiation, the proportion of mature male yearlings was twice as high in those which developed as S0 smolts as compared with those which became S1 smolts. Males destined to mature as yearlings grew more rapidly as underyearlings than immature cohorts. It is concluded that sexual maturation of male chinook salmon is conditional to and facilitated by rapid growth.