Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) 137 INITIATION OF FEEDING DURING HATCHERY REARING OF LANDLOCKED FALL CHINOOK SALMON FRY Michael E. Barnes, William A. Sayler, and Rick J. Cordes South Dakota Department of Game, Fish and Parks McNenny State Fish Hatchery Spearfish, SD 57783 ABSTRACT Hatchery feeding of landlocked fall chinook salmon (Oncorhynchus tshawytscha) fry was initiated at two different stages of development to determine the time to start feeding for optimal fish growth. Despite initially weighing less, fry started on feed at the first visible indication of free-swimming (approximately 20% yolk sac remaining), were significantly heavier after 28 rearing days than fry started on feed at complete yolk sac absorption. Total tank weights were also significantly heavier in the fry started on feed the earliest. No differences in fry mortality were observed between the two feed initiation regimes. For maximum growth, initiating feeding of landlocked fall chinook salmon at the first observation of free-swimming fry is recommended, unless there are overriding fish health concerns. Keywords Oncorhynchus tshawytscha, chinook salmon, salmonid fry, hatchery feeding, swim-up INTRODUCTION Although salmonid fry will begin feeding prior to complete yolk sac absorption (Knight 1963), there are considerable differences of opinion on when to initiate feeding of chinook salmon (Oncorhynchus tshawytscha) and other salmonids during hatchery rearing. The most common practice is to start feeding at fry swim-up, when fry have inflated their swim bladders and absorbed enough yolk sac to maintain a position in the water column (Piper et al. 1982). Needham (1988) also suggested first feeding when fry could swim upright, but then suggested species specific differences in the timing of initial feeding. He gave as a guide initiating feeding of rainbow trout (Oncorhynchus mykiss) fry at 50% of yolk sac remaining, as opposed to only 20% of the yolk sac remaining for initial feeding of Atlantic salmon (Salmo salar). The Alaska Department of Fish and Game (1983) fish culture manual recommends making food available as soon as any salmonid fry swim-up is observed. Contrarily, delayed feeding until near complete yolk-sac absorption
138 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) has been suggested to promote efficient growth and transition to exogenous feeding in rainbow trout (Twongo and MacCrimmon 1976; MacCrimmon and Twongo 1980). Heming et al. (1982) identified an optimal time frame to initiate feeding chinook salmon fry based on incubation water temperatures. Their work was conducted with anadromous salmon in their native range. However, landlocked chinook salmon exhibit substantially different reproductive characteristics, such as egg size, than salmon in their native range (Barnes et al. 2000), which likely make the time frame identified by Heming et al. (1982) unusable with landlocked salmon. Landlocked chinook salmon fry obtained as eggs from Lake Oahe, South Dakota are typically maintained in vertical-tray incubators, moved to rearing tanks just prior to complete absorption of the external yolk sac (button-up), and subsequently started on feed when an estimated 30% of the fry are freeswimming. The impact of the starting feeding at this time on fish growth is uncertain (Palmer et al. 1951; Twongo and MacCrimmon 1976; MacCrimmon and Twongo 1980; Heming et al. 1982). The objective of this study was to determine the effect on the hatchery growth and survival of landlocked chinook salmon fry if feeding is initiated at the first sign of fry swim-up, as compared to initiating feeding at complete yolk sac absorption. METHODS Fry used for this experiment were obtained as eggs during spawning of chinook salmon from Lake Oahe at Whitlocks Spawning Station on October 27, 1999. After fertilization, eggs were pooled during water-hardening and subsequent transport to McNenny State Fish Hatchery, Spearfish, South Dakota. Eggs were incubated in Heath (Flex-a-lite Consolidated, Tacoma, Washington) incubator trays. Fry were removed from the same incubator tray on two dates (January 1 and January 10) corresponding to the first sign of free-swimming fry (approximately 20% of the yolk sac remaining) and near-complete yolk sac absorption. At each date, each of three 100-L cylindrical tanks received 200 fry. Total tank weights were recorded to the nearest g. In addition, 30 fry were individually weighed to the nearest mg. Well water (11º C; total hardness as CaCO 3, 360 mg/l; alkalinity as CaCO 3, 210 mg/l; ph, 7.6; total dissolved solids, 390 mg/l) was used both in the incubator trays and tanks. Flows in each tank were set at 20 L/min throughout the experiment. Hourly hand feeding with #2 BioDiet Starter (Bio-Oregon, Inc., Warrenton, Oregon) was initiated the day after fry were placed in the tanks. Fry were fed to satiation, as indicated by the presence of wasted feed on the bottom of each tank. All food dispensed was recorded to the nearest g. Tanks were cleaned daily to eliminate excess food and fish waste, and any mortalities were removed and recorded at that time. On January 29, 2000, total tank weights were again recorded to the nearest g, and 20 fish from each tank were individually weighed to the nearest mg. Individual fry weight data were analyzed using
Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) 139 Student s t-tests and tank data were analyzed using the Kruskal-Wallis test. Statistical testing was performed using the SPSS (9.0) statistical analysis program (SPSS 1999), with significance pre-determined at P 0.05. RESULTS At the start of the experiment, fry with 20% of their yolk sac remaining weighed significantly less (P = 0.006) than fry which had completely absorbed their visible yolk sacs (Table 1). Despite weighing less at the time of initial feed, at the end of the experiment mean weights from fry started on feed with 20% of their yolk sac remaining were 80 mg more than those fry started on feed 10 days later (P = 0.0001). The improvement in growth of the fry started on feed at the earliest date was also evident in total tank weights and weight gained per tank (Table 2). Mean weights in the tanks started on feed at the first sign of fry swim-up were significantly heavier, by an average of 14 g, than mean weights from the tanks of fry started on feed at complete yolk sac absorption. Weight gain per tank was significantly different, and over 20% greater, in the fry started on feed the earliest. Mean tank mortality ranged from 1 to 7% and was not significantly different between the two feed initiation treatments. Table 1. Mean (± SE) weights (mg) from chinook salmon fry started on feed either at the first observance of free swimming fry (20% yolk sac remaining) or at complete yolk sac absorption. Means in a row are all significantly different at P = 0.05. Weight N First free swimming fry Complete yolk sac absorption Start 30 257 ± 6 z 285 ± 7 y End 60 718 ± 16 z 636 ± 15 y Table 2. Data (mean ± SE) from tanks of chinook salmon fry started on feed either at the first observance of free swimming fry (20% yolk sac remaining) or at complete yolk sac absorption (N = 3). Means in a row followed by the same letter are not significantly different at P = 0.05. First free swimming fry Complete yolk sac absorption Start weight (g) 56 59 End weight (g) 151 + 5 z 137 + 3 y Gain (g) 95 + 5 z 78 + 3 y Food fed (g) 265 + 7 z 281 + 15 z Mortality 8 + 2 z 6 + 4 z
140 Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) DISCUSSION Heming et al. (1982) stated that it would not be beneficial to initiate feeding of chinook salmon fry before 82 incubation days at 11ºC, the point at which 50% of fry in their study were first able to ingest food. In contrast, our earliest feeding started at 67 incubation days, and complete yolk sac absorption occurred on incubation day 76. Heming et al. (1982) also recorded wet weights of approximately 600 mg from non-feeding salmon fry, more than double the weights of fry that we obtained. Obviously the sizes and developmental rates we observed with landlocked fry from Lake Oahe are substantially different than those of chinook salmon in their native range. We believe this is due to the differences in egg size (Barnes et al. 2000), but it could also be due to other, as yet unidentified, environmental factors (Bagenal 1978; Donaldson 1990). Because of these differences, the quantitative models developed by Heming et al. (1982) to identify the time at which initial food presentation to chinook salmon fry should occur do not apply to landlocked chinook salmon fry from Lake Oahe and possibly other freshwater bodies of water. Our results validate the suggestion of Palmer et al. (1951) that salmon should be fed when they are first capable of free swimming if maximum growth is to be attained. The amount of yolk remaining at this stage that they describe appears to be very similar to that which we observed in the early feeding salmon fry from our experiment. Initiating feeding prior to visible yolk sac absorption was also suggested by Heming et al. (1982). Although they found that the optimal time for initial feeding did not coincide with any easily recognizable development stage of chinook salmon fry development, they indicated that such an time occurs well prior to complete yolk sac absorption when fry are reared at 11ºC. Species or strain (domestic vs. wild) differences may explain the disagreement between our results and those reported for rainbow trout (Twongo and MacCrimmon 1976; MacCrimmon and Twongo 1980). Using our smaller experimental tanks, we observed no difference in mortality between fry started on feed at two different developmental times. Wasted feed and fecal material were regularly and easily removed. Starting fry on feed prior to complete swim-up may be a concern in hatcheries with a history of bacterial (environmental) gill disease, particularly if rearing units used for feed initiation are difficult to clean (Post 1987; Warren 1991). RECOMMENDATION We recommend initiating feeding of landlocked chinook salmon lots at the first occurrence of any free-swimming fry, unless there are overriding fish health concerns.
Proceedings of the South Dakota Academy of Science, Vol. 81 (2002) 141 ACKNOWLEDGEMENTS We thank the reference librarians at the South Dakota State Library for their assistance with literature procurement, Kody Steinbrecher and Fritz Fonck for assistance during fish culture. LITERATURE CITED Alaska Department of Fish and Game. 1983. Fish culture manual. Alaska Department of Fish and Game, Juneau. Bagenal, T. B. 1978. Aspects of fish fecundity. Pages 75-101 in S. D. Gerking, editor. Freshwater fish production. Wiley and Sons, New York. Barnes, M. E., R. P. Hanten, R. J. Cordes, W. A. Sayler, and J. Carreiro. 2000. Reproductive performance of inland fall chinook salmon. North American Journal of Aquaculture 62:203-211. Donaldson, E. M. 1990. Reproductive indices as measures of the effects of environmental stressors in fish. Pages 109-122 in S. M. Adams, editor. Biological indicators of stress in fish. American Fisheries Society Symposium 8, Bethesda, Maryland. Heming, T. A., J. E. McInerney, and D. F. Alderdice. 1982. Effect of temperature on initial feeding in alevins of chinook salmon (Oncorhynchus tshawytscha). Canadian Journal of Fisheries and Aquatic Sciences 39:1554-1562. Knight, A. E. 1963. The embryonic and larval development of the rainbow trout. Transactions of the American Fisheries Society 92:344-355. MacCrimmon, H. R., and T. K. Twongo. 1980. Ontogeny of feeding behaviour in hatchery-reared rainbow trout, Salmo gairdneri Richardson. Canadian Journal of Zoology 58:20-26. Needham, T. 1988. Salmon smolt production. Pages 87-116 in L. M. Laird and T. Needham, editors. Salmon and trout farming. Wiley, New York. Palmer, D. D., H. E. Johnson, L. A. Robinson, and R. E. Burrows. 1951. The effect of retardation of the initial feeding on the growth and survival of salmon fingerlings. Progressive Fish-Culturist 13:55-62. Piper, R. G., I. B. McElwain, L. E. Orme, J. P. McCraren, L. G. Fowler, and J. R. Leonard. 1982. Fish hatchery management. U.S. Fish and Wildlife Service, Washington, D.C. Post, G. 1987. Textbook of fish health. T. F. H. Publications, Neptune City, New Jersey. SPSS. 1999. SPSS Base 9.0. SPSS, Inc. Chicago, Illinois. Twongo, T. K., and H. R. MacCrimmon. 1976. Significance of the timing of initial feeding in hatchery rainbow trout, Salmo gairdneri. Journal of the Fisheries Research Board of Canada 33:1914-1921. Warren, J. W. 1991. Diseases of hatchery fish. U.S. Fish and Wildlife Service. Portland, Oregon.