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Hatchery Environment (hatchery + environment)

Distribution by Scientific Domains

Earth and Environmental Science	60%

Selected Abstracts

The relative roles of domestication, rearing environment, prior residence and body size in deciding territorial contests between hatchery and wild juvenile salmon

JOURNAL OF APPLIED ECOLOGY, Issue 3 2003
Neil B. Metcalfe
Summary 1Interactions between captive-reared and wild salmonids are frequent because hatcheries annually rear millions of fish for release in conservation programmes while many thousands of domesticated fish escape from fish farms. However, the outcome of competition between captive-reared and wild fish is not clear: wild fish may be smaller and less aggressive than hatchery fish, but they have more local experience and a prior residence advantage. Moreover, it is important to know whether any competitive differences are genetic (due to the process of domestication) or due to the rearing environment. 2We therefore examined the factors influencing competition for feeding territories in juvenile Atlantic salmon. We studied the effect of domestication by using three independent stocks of both domesticated and wild-origin fish, all of which were reared in a common hatchery environment. We also used fish from the same wild stocks that had been living in the wild. Territorial contests were staged in stream tank compartments between pairs of fish differing in origin or rearing environment; the relative importance of body size and prior residence was also assessed. 3All three stocks of domesticated fish were generally dominant over wild-origin fish when both had been raised in a common hatchery environment. If the wild-origin fish were given a 2-day period of prior residence on the territory this asymmetry in dominance was reversed. However, domesticated fish did not gain any additional advantage from being prior residents. The relative body size of the two contestants had a negligible effect on contest outcomes. 4Truly wild fish (i.e. those of wild origin that had also grown up in the wild) were generally dominant over domesticated or wild-origin fish that had been hatchery-reared. Differences in body size between contestants had no effect on the outcome. 5Synthesis and applications. These results show that, while juvenile farmed Atlantic salmon are inherently more aggressive than wild-origin fish, the hatchery environment reduces their ability to compete for territories with wild resident fish. Rearing salmon in conventional hatcheries for later release into the wild where natural populations already exist may not be a prudent conservation measure; it is preferable to plant eggs or first-feeding fry rather than attempt to ,help' the fish by rearing them through the early life stages. [source]

Overwinter survival of stocked age-0 lake sturgeon

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2009
J. A. Crossman
Summary Knowledge of age-specific survivorship is critical when developing management prescriptions for imperiled species such as the lake sturgeon (Acipenser fulvescens). Management has focused on population restoration through hatchery supplementation, largely in the absence of data about relationships between hatchery rearing conditions, size/age at release, and estimates of overwinter survival for stocked age-0 lake sturgeon. Young of the year lake sturgeon were reared from egg to age 3 months in two separate hatchery environments: a streamside hatchery on the natal Upper Black River, Michigan, and a traditional hatchery environment. From age 3 to 6 months all fish were reared in the traditional hatchery. Fish (n = 20) originating from each rearing environment were surgically implanted with ultrasonic transmitters at 6 months of age (mean total length: 31.4 cm; mean weight: 106.4 g) and released into Black Lake in December 2005. Tracking using manual and automated hydrophones was conducted during April and May 2006 to estimate overwinter survival and to test for differences in survival of fish reared in different hatchery environments. Eighteen fish (45%) were detected, 16 (40%) of which survived the winter (range of distance traveled between observations of surviving fish was 0.09,0.55 km). The remaining fish were not detected. No significant differences in survival were documented due to rearing environment or size at release. This study represents the first quantified estimate of overwinter survival for stocked age-0 lake sturgeon. The minimum estimate of 40% survival through the first winter is encouraging for hatchery programs, and will aid in the development of management prescriptions for this species. [source]

Pigmentation development in hatchery-reared flatfishes

JOURNAL OF FISH BIOLOGY, Issue 5 2000
J. A. Bolker
Malpigmentation is common in hatchery-reared flatfishes, decreasing the market value of whole fish, and increasing the risk of predation for juveniles released to enhance wild stocks. Pigmentation development in flatfishes occurs in two phases. First, during embryonic and larval stages pigment cells differentiate on both sides of the body. Second, at metamorphosis larval melanophores disappear, and adult melanophores differentiate on the ocular but not on the blind side. Malpigmentation seems to result from disruptions of the second phase, and may take the form of albinism on the ocular side or darkening of the blind side. Both types of aberration may be related to aspects of the hatchery environment such as lighting, substratum, and diet. Larval nutrition appears to be a key factor and enrichment of larval diets with fatty acids and Vitamin A can greatly reduce malpigmentation rates; however, levels suffcient to prevent pigmentation defects frequently cause other abnormalities. Two developmental explanations for albinism have been proposed. The first is that differentiation of ocular-side skin follows the normal blind-side pathway and adult melanophores therefore fail to develop on the ocular side. The second hypothesis suggests that dietary deficiencies inhibit retinal development and the resulting visual defects lead to failure of a hormonal signal required for melanophore differentiation. These hypotheses may well be complementary; as yet neither has been thoroughly tested. Definitive tests will require a combination of manipulative techniques such as tissue transplantation and cell culture with nutritional, behavioural and hormonal assays. Such integrative studies will further the understanding both of normal pigmentation development and of the environmental factors that contribute to high rates of albinism in hatchery-reared flatfish. [source]