Development of a Natural Rearing System to Improve Supplemental Fish Quality, 1996-1998 Progress Report.

Abstract

ii EXECUTIVE SUMMARYThis report covers the 1996-1998 Natural Rearing Enhancement System (NATURES) research for increasing hatchery salmon postrelease survival and producing fish with more wildlike behavior, physiology, and morphology prior to release. Experiments were conducted evaluating automatic subsurface feeders; natural diets; exercise systems; seminatural raceway habitat enriched with cover, structure, and substrate; and predator avoidance conditioning for hatchery salmonids. Automatic subsurface feed delivery systems did not affect chinook salmon depth distribution or vulnerability to avian predators. Live-food diets only marginally improved the ability of chinook salmon to capture prey in stream enclosures. A prototype exercise system that can be retrofitted to raceways was developed, however, initial testing indicated that severe amounts of exercise may increase inculture mortality. Rearing chinook salmon in seminatural raceway habitat with gravel substrate, woody debris structure, and overhead cover improved coloration and postrelease survival without impacting in-culture health or survival. Steelhead fry reared in enriched environments with structure, cover, and point source feeders dominated and outcompeted conventionally reared fish. Exposing chinook salmon to caged predators increased their postrelease survival. Chinook salmon showed an antipredator response to chemical stimuli from injured conspecifics and exhibited acquired predator recognition following exposure to paired predator-prey stimuli. The report also includes the 1997 Natural Rearing System Workshop proceedings.NATURES type research is called for in the Columbia Basin Fish and Wildlife Program (sections 7.2D.1-3) and the ESA Snake River Salmon Recovery Plan (sections 4.4.c-d). NATURES can be used to help restore depleted stocks within the Columbia River Basin. Conservation programs may benefit from increased postrelease survival to produce more recruits to the spawning population. Production programs can use NATURES to reduce their impact on wild-reared fish by releasing fewer smolts to negatively interact with wild fish, while maintaining their recruitment levels to the fishery.iii CONTENTS PagePreface v Over the history of the project, the effects of seminatural raceway habitats, automated underwater feeders, exercise current velocities, live food diets, and predator avoidance training have been investigated. The findings of these studies are reported here and in an earlier contract report ). The first section of the current report summarizes the earlier research results. The remainder of the report focuses on research that has been conducted between 1996 and 1998. This includes studies on the effect of seminatural raceway habitat, automated underwater feeders, live food diets, predator avoidance training, and exercise on salmon and steelhead trout. IntroductionTraditionally, salmon (Oncorhynchus spp.) are reared in barren concrete raceways that lack natural substrate, in-stream structure, or overhead cover. The fish are fed in an u...

Environmental enrichment and prior experience of live prey improve foraging behaviour in hatchery‐reared Atlantic salmon

“…These findings are consistent with recommendations made by Maynard et al . (1995, 2001) but here it is apparent that only through a combination of enhancement techniques will post‐release survival be improved. Further work is required to examine all the possible combinations of these techniques in order to maximize post‐release survival with minimal cost to hatcheries.…”

“…Habitat enrichment, whereby pre‐release enclosures are altered to match conditions in the wild by the inclusion of structure and natural substrata (Brown & Day, 2002), has been shown to improve post‐release survival in salmonids (Maynard et al ., 2001). At this stage it is not entirely clear how enrichment helps, but it appears that it induces more naturalistic behaviour in hatchery fishes, including cryptic ( i.e .…”

“…Hatcheries should aim to produce juveniles that are morphologically, genetically, behaviourally and physiologically similar to the stocks they are intended to enhance. Suggested methods for improving the survival of hatchery fishes post-release include supplementary feeding with live foods, the provision of under water feeders, the inclusion of sub-aquatic structure, natural substratum and overhead cover, and brief exposures to predators (Maynard et al, 1995(Maynard et al, , 2001. To date, implementation of the requisite changes in hatchery protocol and technology is very much in its infancy, and the validity and cost effectiveness of pre-release training has yet to be fully evaluated.…”

Wild origin and enriched environment promote foraging rate and learning to forage on natural prey of captive reared Atlantic salmon parr

“…(2007), Brockmark & Johnsson (2010), Chittenden et al. (2010) and Salvanes & Braithwaite (2005) addressed slightly different questions than our study, all studies together demonstrate that multiple features in the physical environment of hatcheries should be altered to resemble natural conditions as far as possible, enabling fish to develop and express natural behaviour (Maynard et al. 1996).…”

“…Multiple alterations in the rearing environment were also found to give strongest behavioural changes in Atlantic cod (Gadus morhua L.) . Even though the studies of Brockmark et al (2007), , Chittenden et al (2010) and addressed slightly different questions than our study, all studies together demonstrate that multiple features in the physical environment of hatcheries should be altered to resemble natural conditions as far as possible, enabling fish to develop and express natural behaviour (Maynard et al 1996).…”