Wild Parr Research Articles

Alternative male life‐history tactics as potential vehicles for speeding introgression of farm salmon traits into wild populations

AbstractReleases of cultured organisms, such as farm Atlantic salmon (Salmo salar L.), threaten native biodiversity and the integrity of natural communities. Salmon escaping from sea farms, however, have relatively poor reproductive success, suggesting that the rate of spread of domesticated traits may be reduced. We now compare the relative reproductive success of males that mature precociously in freshwater (parr) and find that those of farm origin have higher breeding and fertilization success than wild and hybrid individuals. Specifically, hybrid parr had 57% and wild parr 25% the success of farm parr. Early maturing males could thus be important vehicles promoting introgression of domesticated and/or non‐native traits into wild populations and ultimately have long‐term impact on the genetic integrity of native populations.

High mortality in introduced brown trout depressed potential gene flow to a wild population

Hatchery reared 0+ year brown trout Salmo trutta, with 51 mm mean LT, were released in a sea trout stream in June 1991 to compare the survival of wild and introduced trout during the freshwater stage from age 0+ to 2+ years. The introduced brown trout were homozygous for a genetic marker, enabling released individuals and their offspring to be distinguished phenotypically from the local sea trout. The mean size of 0+ and 1+ year introduced parr was larger than 0+ and 1+ year wild parr, while 2+ year parr of both groups were of the same size. Half year survival rates of both introduced and wild parr increased with size up to c. 80 mm (1+ years), but then decreased, and could be described by a polynomial regression function, with the same shape for both groups. The introduced parr had, however, a significant lower survival rate than the wild parr. The number of the introduced cohort decreased from 2200 at release in 1991 to c. 20 in March 1994 (c. 1% of the original number). Between 1994 and 2000 no introduced individuals or offspring have been observed in the study area. High mortality at the parr stage and additional mortality until the spawning, give a low probability for a genetic impact on the local population as long as releases are restricted, both in time and number of fish.

Influence of sexual maturity on feeding, growth and energy stores of wild Atlantic salmon parr

Influence of sexual maturity on feeding, growth and energy stores of wild Atlantic salmon parr

Effects of Floy and Soft VIalpha Tags on Growth and Survival of Juvenile Arctic Char

Abstract The Floy FTF-69 fingerling tag and the new soft VIalpha (VI) tag can both be used on small fish (>100 mm and >150 mm, respectively) according to their manufacturers, but information on their use and effect on fish has not been available. In this study, these two tags were compared for one year on wild Arctic char Salvelinus alpinus, parr (lake dwelling), and smolts (100–229 mm) from two small lakes in northern Norway. Comparisons of growth rate, survival, and tag retention were analyzed. In general, VI-tagged smolts grew significantly better than Floy-tagged smolts in the sea. However, the difference was largest for the smallest fish (100–189 mm); for the larger fish (190–229 mm), there was less or no difference. Survival rates in the sea were also significantly higher (11–15%) for the smallest (<170 mm) VI-tagged smolts than for Floy-tagged smolts of the same size; larger VI-tagged smolts (≥170 mm) only survived at a slightly higher (1.5–4.0%) and nonsignificant rate than corresponding Floy-tagg...

Post‐release adaptation processes of hatchery‐reared honmasu salmon parr

Hatchery‐reared honmasu salmon Oncorhynchus rhodurus × masou parr released into the Yanagisawa River, Tochigi Prefecture on 24 June 1996 increased significantly in length and weight by November, while siblings retained in hatchery tanks did not. Plasma growth hormone (GH) levels of the released parr increased from 1 day after the release until 23 August, while the GH levels of the wild parr in the river did not increase. The released parr started to consume various natural prey organisms within a day after release. However, stomach fullness of the released parr was considerably lower than that of the wild parr during the first week following release. Trypsin activity in the released parr increased after 23 August, 2 months post‐release. The results demonstrate that the released parr adapt to the natural river environment within weeks. Endocrine control by GH and exocrine pancreas activity appear to play important roles in the post‐release adaptation processes.

Spatial and temporal covariation in the recruitment and abundance of Atlantic salmon populations in the Baltic Sea

Synchronous trends in the abundance of hatchery and wild Baltic salmon populations are examined using correlation analysis. The river catch of wild adult salmon, the recruitment of age 0+ wild salmon parr, and the recapture rate of tagged hatchery smolts are positively correlated among rivers in the Baltic Sea. The spatial correlation among populations is greater than reported for other anadromous salmonids. Baltic salmon populations have undergone low frequency, high amplitude changes in abundance during the past 200 years. Recent production levels have been supported largely by hatcheries. EVorts to conserve the remaining wild populations through fisheries regulation appear to be having a positive eVect on spawner abundance. ? 1999 International Council for the Exploration of the Sea

Population structure of Atlantic salmon from the Conne River, Newfoundland as determined from microsatellite DNA

Variation at four microsatellite loci was examined for three populations of Atlantic salmon Salmo salar from the Conne River, Newfoundland. Samples of wild parr were collected from the mainstem Conne River during 4 years, and from tributaries Twillick Brook and Bernard Brook during 2 years. No significant temporal variation was observed in allele frequencies at the Ssal4, Ssal97, Ssa202, and Ssa289 loci. No difference in allele frequencies was observed between parr from Bernard and Twillick brooks at any locus, but allele frequencies of mainstem Conne River parr were significantly different from those of the tributaries at Ssal4 and Ssa202, indicative of differentiation among local populations. Atlantic salmon from the Conne River system were well differentiated from those in Nova Scotia, Canada and from those in Europe.

Relative ventricular weight of wild Atlantic salmon parr in relation to sex, gonad maturation and migratory activity

Relative ventricular weight (RVW, ventricular weight/body weight · 100) was measured for five groups of Atlantic salmon parr from the Girnock Burn in Scotland. The mean RVW was: mature males, 0.087; immature resident males, 0.054; immature resident females, 0.056; immature migrant males, 0.056; immature migrant females, 0.053. For a group of mature male parr from the R. Nith, Galloway, Scotland, the mean RVW was 0.108. There were no significant differences in the RVW between groups of immature fish. The RVW of each group of mature male parr was significantly greater than those of each, group of immature parr. Condition indices (weight/length3) were closely similar between all groups of parr. The functional significance of plasticity in ventricular weight is discussed in relation to life histories of Atlantic salmon.

Relative ventricular weight of wild Atlantic salmon parr in relation to sex, gonad maturation and migratory activity

Relative ventricular weight of wild Atlantic salmon parr in relation to sex, gonad maturation and migratory activity

Homing of Atlantic salmon: effects of juvenile learning on transplanted post-spawners

When cultured Atlantic salmon are released into nature, they compete with wild fish for food, space, and breeding partners. As a result of morphological, physiological, ecological, and behavioural changes that occur in hatcheries, their comp etitive ability often differs from that of wild fish. These changes are partly phenotypic and partly genetic. Cultured juveniles' faster growth rate influences age and size at smolting and maturity, reproductive output, and longevity. Fast-growing parr tend to smolt younger, produce more but smaller eggs, attain maturity earlier, and die younger. Juvenile learning influences a number of behavioural traits, and differences in early experience appear to affect feeding and spawning success, migratory behaviour, and homing ability. Genetic change in hatcheries is chiefly the result of natural selection, with differential mortality among genotypes and broodstock selection based on production traits such as high adult body mass and fast growth rate. Experimental evidence has revealed that cultured parr's greater aggression often allows them to dominate wild parr, although smaller cultured parr can be subordinated if they co-occur in fast-flowing water and if wild smolts have established prior residence. During spawning, the fitness of wild salmon is superior to that of cultured conspecifics. Cultured males are inferior to wild males in intra-sexual competition, courting, and spawning; cultured females have greater egg retention, construct fewer nests, and are less efficient at covering their eggs in the substratum than their wild counterparts. In rivers, the early survival of cultured offspring is lower than that of their wild counterparts. The lifetime reproductive success of farmed fish has been estimated at 17% that of similar-sized wild salmon. As a result of ecological interaction and through density-dependent mechanisms, cultured fish may displace wild conspecifics to some extent, increase their mortality, and decrease their growth rate, adult size, reproductive output, biomass, and production.

Plasma Thyroid Hormone Levels in Migratory and Lake-Resident Coho Salmon Juveniles from the Karluk River System, Alaska

This study tested the hypothesis that thyroid hormone levels in wild juvenile coho salmon Oncorhynchus kisutch are higher in fish beginning their seaward migration (smolts) than in lake-resident fish (parr). Average overall thyroxine (T4) levels were higher in wild smolts (3.5 ng/mL) than in wild parr (1.8 ng/mL); however, average overall triiodothyronine (T3) levels were similar in wild smolts (3.0 ng/mL) and parr (2.3 ng/mL). Whereas hormone levels in smolts varied between sampling dates (mean T4, 1.2–6.6 ng/mL; mean T3, 0.7–4.8 ng/mL; P < 0.05), hormone levels in parr remained fairly constant (mean T4, 1.3–2.6 ng/mL; mean T3, 1.8–2.8 ng/mL; P > 0.05). Partly because of these dissimilar patterns of variability, differences in thyroid hormone levels between smolts and parr tended to be subtle. Thus, wild coho smolts were more similar to wild parr than might have been predicted from studies of hatchery-reared fish. Furthermore, because hormone levels in migrants were sometimes similar to those in nonmigrants, predictions of the onset of the seaward migration by wild coho salmon probably should be based on more factors than thyroid hormone levels alone.

Responses of juvenile and sexually mature two-summer-old salmon ( Salmo salar L.) to prolonged swimming

Two-summer-old juvenile and sexually mature Atlantic salmon were forced to swim for 0.5, 1, 2, 4, 8 or 12 h at 50 cm/s (ca. 2.5 body length/s). Collapsed fish and fish swimming the whole test time were sampled for physiological analyses. Both the juvenile and mature fish exhibited an initial stress response to increased flow, as shown by the elevated plasma cortisol and lactate concentrations and by the changes in erythrocytic ATP and chloride concentrations. The physiological state of the mature males recovered well within 2–4 h of swimming. In contrast, the juveniles had continuously high plasma cortisol and lactate values with a large individual variation, indicating that the energy production for swimming was partially anaerobic. The collapsed fish showed clear signs of anaerobic metabolism. The results indicate that the aerobic capacity for prolonged swimming is lowered in juvenile salmon also beyond the time of smolt migration, whereas the mature males have a swimming capacity similar to wild parr. However, the responses of juvenile salmon to swimming in autumn are not similar to those observed on migrating smolt.

Feeding by Hatchery-Reared and Wild Atlantic Salmon (Salmo salar) Parr in Streams

Hatchery-reared Atlantic salmon (Salmo salar) parr were captured 1–3 mo after release in streams, along with wild parr from the same streams. Identification of their stomach contents showed total number of organisms and number of taxa per stomach were greater and there was a higher index of stomach fullness in wild than in hatchery parr resident ≤ 2 mo in a stream. Wild parr consumed more Brachycentridae, Hydroptilidae, Diptera, and Plecoptera than did hatchery parr, but sometimes less Odontoceridae and Heptageniidae. These differences may have arisen from size-dependent food selection, the effects of feeding experience, or possible microhabitat differences between wild and hatchery parr. Key words: salmon parr, hatchery-reared, wild, feeding

Histological Comparisons of the Adrenal-Cortical Cells of Hatchery and Wild Landlocked Atlantic Salmon (Salmo salar)

No differences were found in mean diameters of adrenal-cortical cell nuclei between hatchery parr of landlocked Atlantic salmon (Salmo salar) killed immediately after removal from hatchery rearing pools and wild parr electrofished in two streams, and between hatchery and wild parr held for various periods in an outdoor stream aquarium simulating natural conditions. The similarities suggested that the wild and hatchery parr were similar in physiological response to environmental stress. In both hatchery and wild parr, the diameters differed at different times, indicating a downward trend from May to August in the one year of the study. No consistent relation was found between nucleus diameter and social behavior.

Greater Dispersal of Wild Compared with Hatchery-Reared Juvenile Atlantic Salmon Released in Streams

When wild juvenile (parr) Atlantic salmon (Salmo salar L.) caught by electrofishing, and an equal number of hatchery-reared parr, matched for size with the wild ones, were released at three sites in unfamiliar streams containing resident parr, more hatchery-reared than wild parr could be observed by skin-diving in the areas 1 and 2 weeks later.Observed mortalities of wild parr were not sufficiently higher than those of hatchery parr to explain this result. Nor could a higher proportion of wild parr be found hiding compared with hatchery parr when one release site was electrofished a week after the release. Wild parr were found in greater numbers at points farther from one of the release sites than were hatchery-reared parr, and also more wild fish passed through a salmon counting fence approximately 100 m from a fourth release site than did hatchery-reared parr.This greater dispersal of wild parr from the release site compared with hatchery parr has important consequences to estimates of comparative survival between the two stocks.