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1.
One of the strategies that can be used to reduce predation impacts to valued fish species is by swamping predators with more
prey than they can eat. We examined whether this approach was viable by calculating the maximum bioenergetic consumption potential
of non-native smallmouth bass Micropterus dolomieu on fall Chinook salmon Oncorhynchus tshawytscha juveniles in the Yakima River throughout the spring between 1998 and 2002 and comparing those estimates to previously published
estimates of fall Chinook salmon consumption. We found that the smallmouth bass population consumed fall Chinook salmon well
below their bioenergetic potential. However, individual smallmouth bass that were piscivorous were eating other food items
at a level near satiation. Furthermore, the maximum consumption potential was relatively low prior to mid-April, and then
increased substantially to a peak in May. Predation mortality to hatchery fall Chinook salmon could be reduced within a year
by releasing hatchery fall Chinook salmon that will emigrate quickly prior to mid-April, when predation potential is still
very low. However, attempting to swamp predators with hatchery Chinook salmon to benefit naturally produced Chinook salmon
poses uncertain benefits to natural origin fish and likely unacceptable costs to hatchery fish. Considerable swamping is occurring
by other naturally produced fish species in the Yakima River such as dace Rhinichthys spp., mountain whitefish Prosopium williamsoni, and crayfish Pacificastus spp. Therefore, it is important to consider impacts to these non-target species because they could have indirect predation
impacts on Chinook salmon. 相似文献
2.
Todd N. Pearsons Andrew R. Murdoch Greg Mackey Keely G. Murdoch Tracy W. Hillman Matthew R. Cooper Joseph L. MIller 《Environmental Biology of Fishes》2012,94(1):87-100
Ecological risks of Pacific salmon (spring, summer, and fall run Chinook, coho, and sockeye salmon) and steelhead trout hatchery
programs operated between 2013 and 2023 in the Upper Columbia Watershed will be assessed using Delphi and modeling approaches.
Committees composed of resource managers and public utility districts identified non-target taxa of concern (i.e., taxa that
are not the target of supplementation), and acceptable hatchery impacts (i.e., change in population status) to those taxa.
Biologists assembled information about hatchery programs, non-target taxa, and ecological interactions and this information
will be provided to expert panelists in the Delphi process to facilitate assessment of risks and also used to populate the
Predation, Competition, and Disease (PCD) Risk 1 model. Delphi panelists will independently estimate the proportion of a non-target
taxa population that will be affected by each individual hatchery program. Estimates from each of the two approaches will
be independently averaged, a measure of dispersion calculated (e.g., standard deviation), and subsequently compared to the
acceptable hatchery impact levels that were determined previously by committees of resource managers and public utility districts.
Measures of dispersion will be used to estimate the scientific uncertainty associated with risk estimates. Delphi and model
results will be compared to evaluate the qualities of the two approaches. Furthermore, estimates of impacts from each hatchery
program will be combined together to generate an estimate of cumulative impact to each non-target taxon. 相似文献
3.
Overview of salmon stock enhancement in southeast Alaska and compatibility with maintenance of hatchery and wild stocks 总被引:1,自引:0,他引:1
Modern salmon hatcheries in Southeast Alaska were established in the 1970s when wild runs were at record low levels. Enhancement
programs were designed to help rehabilitate depressed fisheries and to protect wild salmon stocks through detailed planning
and permitting processes that included focused policies on genetics, pathology, and management. Hatcheries were located away
from significant wild stocks, local sources were used to develop hatchery broodstocks, and juveniles are marked so management
can target fisheries on hatchery fish. Initially conceived as a state-run system, the Southeast Alaska (SEAK) program has
evolved into a private, non-profit concept centered around regional aquaculture associations run by fishermen and other stakeholders
that pay for hatchery operations through landing fees and sale of fish. Today there are 15 production hatcheries and 2 research
hatcheries in SEAK that between 2005 and 2009 released from 474 to 580 million (average 517 million) juvenile salmon per year.
During this same period commercial harvest of salmon in the region ranged from 28 to 71 million salmon per year (average 49
million). Contributions of hatchery-origin fish to this harvest respectively averaged 2%, 9%, 19%, 20%, and 78% for pink,
sockeye, Chinook, coho, and chum salmon. Both hatchery and wild salmon stocks throughout much of Alaska have experienced high
marine survivals since the 1980s and 1990s resulting in record harvests over the past two decades. Although some interactions
between hatchery salmon and wild salmon are unavoidable including increasing concerns over straying of hatchery fish into
wild salmon streams, obvious adverse impacts from hatcheries on production of wild salmon populations in this region are not
readily evident. 相似文献
4.
Maureen A. Hess Craig D. Rabe Jason L. Vogel Jeff J. Stephenson Doug D. Nelson Shawn R. Narum 《Molecular ecology》2012,21(21):5236-5250
While supportive breeding programmes strive to minimize negative genetic impacts to populations, case studies have found evidence for reduced fitness of artificially produced individuals when they reproduce in the wild. Pedigrees of two complete generations were tracked with molecular markers to investigate differences in reproductive success (RS) of wild and hatchery‐reared Chinook salmon spawning in the natural environment to address questions regarding the demographic and genetic impacts of supplementation to a natural population. Results show a demographic boost to the population from supplementation. On average, fish taken into the hatchery produced 4.7 times more adult offspring, and 1.3 times more adult grand‐offspring than naturally reproducing fish. Of the wild and hatchery fish that successfully reproduced, we found no significant differences in RS between any comparisons, but hatchery‐reared males typically had lower RS values than wild males. Mean relative reproductive success (RRS) for hatchery F1 females and males was 1.11 (P = 0.84) and 0.89 (P = 0.56), respectively. RRS of hatchery‐reared fish (H) that mated in the wild with either hatchery or wild‐origin (W) fish was generally equivalent to W × W matings. Mean RRS of H × W and H × H matings was 1.07 (P = 0.92) and 0.94 (P = 0.95), respectively. We conclude that fish chosen for hatchery rearing did not have a detectable negative impact on the fitness of wild fish by mating with them for a single generation. Results suggest that supplementation following similar management practices (e.g. 100% local, wild‐origin brood stock) can successfully boost population size with minimal impacts on the fitness of salmon in the wild. 相似文献
5.
Kathryn Kostow 《Reviews in Fish Biology and Fisheries》2009,19(1):9-31
State and federal agencies in the United States annually release millions of hatchery salmon and steelhead into public waters.
Many of the hatchery programs are located in areas where the wild populations are now listed under the U.S. Endangered Species
Act (ESA) (16 U.S.C. §§ 1531–1544). These hatchery programs pose genetic and ecological risks to wild fish populations. Genetic
risks occur when hatchery and wild fish interbreed and usually occur within a taxonomic species. Ecological risks occur when
the presence of hatchery fish affects how wild fish interact with their environment or with other species and may affect whole
species assemblages. This paper reviews some of the factors that contribute to ecological risks. Important contributing factors
include the relative abundance of hatchery and wild fish in natural production areas, hatchery programs that increase density-dependant
mortality, residual hatchery fish, some physical advantages that hatchery fish can have over wild fish, and life history characteristics
that may make some species especially vulnerable to the effects of ecological risks. Many of these risk factors can be mitigated
by management activities that reduce the level of interactions between hatchery and wild fish. This paper concludes by recommending
twelve mitigation strategies that may be useful when agencies need to bring hatchery programs into compliance with the take
provisions of the ESA. 相似文献
6.
Aggregate hatchery production of Pacific salmon in the Kamchatka region of the Russian Federation is very low (< 0.5% of total
harvest, with five hatcheries releasing approximately 41 M juvenile salmon annually), but contributions in certain rivers
can be substantial. Enhancement programs in these rivers may strongly influence fitness and production of wild salmon. In
this paper we document significant divergence in demographic traits in hatchery salmon populations in the Bolshaya River and
we estimate the proportion of hatchery chum salmon in the total run in the Paratunka River to demonstrate the magnitude of
enhancement in this system. We observed a reduction in the expression of life history types in hatchery populations (ranging
from 1 to 9 types) compared to wild populations (17 types) of sockeye salmon in the Bolshaya River. We found similar trends
in Chinook salmon in the same river system. This reduced life history diversity may make these fish less resilient to changes
in habitat and climate. We estimate hatchery chum salmon currently contribute 17-45% to the natural spawning population in
the Paratunka River. As hatchery fish increase in numbers at natural spawning sites, this hatchery production may affect wild
salmon production. It is important to investigate the risk of introgression between hatchery and wild salmon that can lead
to reduction in salmon fitness in Kamchatka rivers, as well as the potential of ecological interactions that can have consequences
on status of wild salmon and overall salmon production in this region. 相似文献
7.
Early marine trophic interactions of wild and hatchery chum salmon (Oncorhynchus keta) were examined as a potential cause for the decline in harvests of adult wild chum salmon in Taku Inlet, Southeast Alaska.
In 2004 and 2005, outmigrating juvenile chum salmon were sampled in nearshore habitats of the inlet (spring) and in epipelagic
habitat at Icy Strait (summer) as they approached the Gulf of Alaska. Fish were frozen for energy density determination or
preserved for diet analyses, and hatchery stocks were identified from the presence of thermal marks on otoliths. We compared
feeding intensity, diets, energy density, and size relationships of wild and hatchery stocks (n = 3123) across locations and weeks. Only hatchery fish feeding intensity was negatively correlated with fish abundance. In
both years, hatchery chum salmon were initially larger and had greater energy density than wild fish, but lost condition in
early weeks after release as they adapted to feeding on wild prey assemblages. Diets differed between the stocks at all inlet
locations, but did not differ for hatchery salmon between littoral and neritic habitats in the outer inlet, where the stocks
overlapped most. Both diets and energy density converged by late June. Therefore, if density-dependent interactions affect
wild chum salmon, these effects must be very rapid because survivors in Icy Strait showed few differences. Our study also
demonstrates that hatchery release strategies used near Taku Inlet successfully promote early spatial segregation and prey
partitioning, which reduce the probability of competition between wild and hatchery chum salmon stocks. 相似文献
8.
Kathryn Kostow 《Environmental Biology of Fishes》2012,94(1):285-310
The Pacific Northwest state and federal agencies and tribes that operate salmon and steelhead (Oncorhynchus sp.) hatcheries are authorized to develop and implement strategies to reduce the risks the programs pose to wild fish populations.
This paper reviews five case studies from the states of Oregon and Washington, USA, where agencies and tribes have implemented
or proposed programs that were intended to reduce ecological risks due to hatchery programs. The case studies are for Oregon
coho salmon, Select Area terminal fisheries programs for Chinook and coho salmon in the lower Columbia River, Hood Canal chum
salmon in Puget Sound Washington, Siletz River steelhead on the Oregon coast, and Okanogan River Chinook salmon in eastern
Washington. The five case studies address a diversity of management objectives and species. They demonstrate some of the science
and risk reduction strategies used to alleviate the ecological effects of hatcheries, and they document some of the results
and outcomes of taking action. Elements of four of the case studies have been in place for nearly 20 years. The available
science and the conservation ethic toward hatchery programs evolved significantly over this period, and management decisions
and strategies have been influenced by public policy as well as by scientific information. Therefore the case studies also
document some of the history, the evolution of ideas, the uncertainty, and the political controversy associated with the management
of this risk factor. The paper concludes with six principles to help guide the development of future risk reduction programs. 相似文献
9.
Levin PS Zabel RW Williams JG 《Proceedings. Biological sciences / The Royal Society》2001,268(1472):1153-1158
Hatchery programmes for supplementing depleted populations of fish are undergoing a worldwide expansion and have provoked concern about their ramifications for populations of wild fish. In particular, Pacific salmon are artificially propagated in enormous numbers in order to compensate for numerous human insults to their populations, yet the ecological impacts of this massive hatchery effort are poorly understood. Here we test the hypothesis that massive numbers of hatchery-raised chinook salmon reduce the marine survival of wild Snake River spring chinook, a threatened species in the USA. Based on a unique 25-year time-series, we demonstrated a strong, negative relationship between the survival of chinook salmon and the number of hatchery fish released, particularly during years of poor ocean conditions. Our results suggest that hatchery programmes that produce increasingly higher numbers of fish may hinder the recovery of depleted wild populations. 相似文献
10.
Richard E. Brenner Steve D. Moffitt William S. Grant 《Environmental Biology of Fishes》2012,94(1):179-195
The straying of hatchery salmon may harm wild salmon populations through a variety of ecological and genetic mechanisms. Surveys
of pink (Oncorhynchus gorbuscha), chum (O. keta) and sockeye (O. nerka) salmon in wild salmon spawning locations in Prince William Sound (PWS), Alaska since 1997 show a wide range of hatchery
straying. The analysis of thermally marked otoliths collected from carcasses indicate that 0–98% of pink salmon, 0–63% of
chum salmon and 0–93% of sockeye salmon in spawning areas are hatchery fish, producing an unknown number of hatchery-wild
hybrids. Most spawning locations sampled (77%) had hatchery pink salmon from three or more hatcheries, and 51% had annual
escapements consisting of more than 10% hatchery pink salmon during at least one of the years surveyed. An exponential decay
model of the percentage of hatchery pink salmon strays with distance from hatcheries indicated that streams throughout PWS
contain more than 10% hatchery pink salmon. The prevalence of hatchery pink salmon strays in streams increased throughout
the spawning season, while the prevalence of hatchery chum salmon decreased. The level of hatchery salmon strays in many areas
of PWS are beyond all proposed thresholds (2–10%), which confounds wild salmon escapement goals and may harm the productivity,
genetic diversity and fitness of wild salmon in this region 相似文献
11.
The use of developmental instability (an individual's failure to produce a consistent phenotype in a given environment) was evaluated to detect the effects of outplanting hatchery fish on wild salmon. Juvenile chinook salmon were collected in 1989, 1990, and 1991 from five drainages in the Snake River Basin. In each drainage we attempted to collect fish from streams with no hatchery supplementation (wild), naturally spawning fish from streams with hatchery supplementation (natural), and fish collected at a hatchery. Forty fish were collected per site and the number of elements in bilateral characters were counted on each side of the fish. Indices of fluctuating asymmetry (FA), a measure of minor, random deviations in perfect symmetry of bilateral counts, were calculated as an estimator of developmental instability. Analysis of character counts from seven paired characters revealed normal distributions. Only one of the characters displayed counts that were statistically larger on one side than the other, indicating that directional asymmetry (DA) or antisymmetry was not a major bias of FA. However, the means of all individual characters revealed a non-statistically significant left side bias. We analyzed our data using two indices of FA (FA1 and FA5) with different levels of sensitivity to DA. Differences in both FA indices were found among years, with collection sites in 1989 having significantly larger FA values than in 1991 (FA p < 0.01). Levels of FA among wild, natural, and hatchery fish were comparatively small (FA1 p = 0.17). This suggests developmental conditions were different in the first year of the study than in the last. The cause of these differences may be linked to either genetic or environmental variation or to gene—environment interactions, but the general population declines of salmon that occurred during this time obscures more specific conclusions. 相似文献
12.
Barry A. Berejikian Donald A. Larsen Penny Swanson Megan E. Moore Christopher P. Tatara William L. Gale Chris R. Pasley Brian R. Beckman 《Environmental Biology of Fishes》2012,94(1):29-44
Wild steelhead (Oncorhynchus mykiss) typically spend two or more years in freshwater before migrating to sea, but hatchery steelhead are almost ubiquitously
released as yearlings. Their large size at release coupled with life history pathways that include both male and female maturation
in freshwater present ecological risks different from those posed by hatchery populations of Pacific salmon. Yearling hatchery
reared steelhead that fail to attain minimum thresholds for smoltification or exceed thresholds for male maturation tend to
‘residualize’ (i.e., remain in freshwater). Residuals pose ecological risks including size-biased interference competition
and predation on juvenile salmon and trout. Three hatchery populations of steelhead in Hood Canal, WA were reared under growth
regimes designed to produce a more natural age at smoltification (age-2) to aid in rebuilding their respective natural populations.
Mean smolt sizes and size variability at age-2 were within the range of wild smolts for two of the three populations. The
third population reared at a different facility under similar temperatures exhibited high growth rate variability and high
male maturation rates (20% of all released fish). Experimentally comparing age-1 and age-2 smolt programs will help identify
optimal rearing strategies to reduce the genetic risk of domestication selection and reduce residualism rates and associated
negative ecological effects on natural populations. Investigations of Winthrop National Fish Hatchery summer-run steelhead
will measure a) selection on correlated behavioral traits (‘behavioral syndromes’), b) degree of smoltification, c) changes
in hormones that regulate gonad growth at key developmental stages, and d) conduct extensive post-release monitoring of fish
reared under each growth regime. 相似文献
13.
Genetic interactions between marine finfish species in European aquaculture and wild conspecifics 总被引:2,自引:0,他引:2
The principal species of marine aquaculture in Europe are Atlantic salmon (Salmo salar), sea bass (Dicentrarchus labrax) and sea bream (Sparus auratus). For Atlantic salmon and sea bass, a substantial part of total genetic variation is partitioned at the geographical population level. In the case of sea bream, gene flow across the Azores/Mediterranean scale appears to be extensive and population structuring is not detected. For Atlantic salmon and sea bass, natural population structure is at risk from genetic interaction with escaped aquaculture conspecifics. The locally adaptive features of populations are at risk from interbreeding with non‐local aquaculture fish. Wild populations, generally, are at risk from interactions with aquaculture fish that have been subject to artificial selection or domestication. Atlantic salmon is the main European aquaculture species and its population genetics and ecology have been well‐studied. A general case regarding genetic interactions can be based on the information available for salmon and extended to cover other species, in the appropriate context. A generalized flow chart for interactions is presented. Salmon escape from aquaculture at all life stages, and some survive to breed among wild salmon. Reproductive fitness in the escaped fish is lower than in native, wild fish because of behavioural deficiencies at spawning. However, as the number of salmon in aquaculture greatly exceeds the number of wild fish, even small fractional rates of escape may result in the local presence of large numbers, and high frequencies, of escaped fish. At present, policy and legislation in relation to minimizing genetic interactions between wild and aquaculture fish is best developed for Atlantic salmon, through the recommendations of the Oslo Agreement developed by the North Atlantic Salmon Conservation Organization and subsequent agreements on their implementation. In future, the potential use of genetically modified fish in aquaculture will make additional policy development necessary. Improved containment is recommended as the key to minimizing the numbers and therefore the effects of escaped fish. Emergency recovery procedures are recommended as a back‐up measure in the case of containment failure. Reproductive sterility is recommended as a future key to eliminating the genetic potential of escaped fish. The maintenance of robust populations of wild fish is recommended as a key to minimizing the effects of escaped fish on wild populations. 相似文献
14.
PCD RISK 1 is a flexible computer model designed to assist in assessment and reduction of ecological risks to natural origin
fish from hatchery fish releases. PCD RISK 1 simulates predation, competition, and disease impacts on naturally produced salmonids
caused by hatchery smolts in fresh water as they move downstream or residualize after release. Individual- based, the model
relies upon user specified inputs of up to 45 variables, such as number and size of hatchery and wild fish, and water temperature.
The model generates hatchery and natural fish of specified size distributions, then randomly pairs them for interactions for
a specified number of days and encounters. Wild fish are subjected to predation if they are less than 50% the length of hatchery
fish, otherwise they are subjected to competition. After all of the allowable competition and predation occurs, survivors
are subjected to disease risk. The model can provide either deterministic or probabilistic output. Deterministic output includes
the number and proportion of wild fish that die from predation, competition, disease, and from all interactions combined.
Probabilistic output includes probability distributions of the number and proportion of mortalities, based on user-specified
uncertainty input either as uniform or triangular distributions for any of several variables. If desired, the model can also
quantify impacts for multiple age or size classes. Simulations of a variety of hatchery programs reveal that risks are highly
diverse and that a variety of options are available to reduce risks. 相似文献
15.
Mitsuhiro Nagata Yasuyuki Miyakoshi Hirokazu Urabe Makoto Fujiwara Yoshitaka Sasaki Kiyoshi Kasugai Mitsuru Torao Daisei Ando Masahide Kaeriyama 《Environmental Biology of Fishes》2012,94(1):311-323
The chum and pink salmon catches in Hokkaido, Japan have increased dramatically since the 1970s and the 1990s, respectively.
In contrast, masu salmon catches have been steadily decreasing. Despite intensive hatchery development in Hokkaido, naturally
spawning salmon populations persist based on results from a recent river survey. This paper focuses on the challenges of maintaining
hatchery salmon populations while protecting natural chum, pink and masu salmon populations in Hokkaido. Two important initiatives
related to meeting this ambitious goal are managing hatcheries in a way that minimizes negative interactions between natural
and hatchery salmon populations, and initiating new efforts at restoring and rehabilitating degraded freshwater habitats.
In addition, in order to maintain a balance of demand and supply in the domestic market through the exportation of extra salmon,
Hokkaido has decided to enter full assessment to gain Marine Stewardship Council (MSC) certification of the Hokkaido chum
salmon trap net fishery. This would involve a fundamental shift in fisheries management as practiced in Japan, specifically
elevating the importance of managing the fishery in a way that conserves natural salmon populations. A key component of a
new salmon management strategy is the establishment of a zone management framework based on the designation of stream units
to spatially separate natural salmon from hatchery salmon to minimize negative effects of hatchery fish and to utilize effectively
hatchery salmon for commercial fisheries. This effort is allied with similar initiatives in other Pacific Rim countries that
are focusing on management reform to restore natural ecosystem function and maintain the coexistence of wild and hatchery
salmon. 相似文献
16.
Elizabeth A. Daly Richard D. Brodeur Joseph P. Fisher Laurie A. Weitkamp David J. Teel Brian R. Beckman 《Environmental Biology of Fishes》2012,94(1):117-134
Ecological interactions between natural and hatchery juvenile salmon during their early marine residence, a time of high mortality, have received little attention. These interactions may negatively influence survival and hamper the ability of natural populations to recover. We examined the spatial distributions and size differences of both marked (hatchery) and unmarked (a high proportion of which are natural) juvenile Chinook salmon in the coastal waters of Oregon and Washington from May to June 1999–2009. We also explored potential trophic interactions and growth differences between unmarked and marked salmon. Overlap in spatial distribution between these groups was high, although catches of unmarked fish were low compared to those of marked hatchery salmon. Peak catches of hatchery fish occurred in May, while a prolonged migration of small unmarked salmon entered our study area toward the end of June. Hatchery salmon were consistently longer than unmarked Chinook salmon especially by June, but unmarked salmon had significantly greater body condition (based on length-weight residuals) for over half of the May sampling efforts. Both unmarked and marked fish ate similar types and amounts of prey for small (station) and large (month, year) scale comparisons, and feeding intensity and growth were not significantly different between the two groups. There were synchronous interannual fluctuations in catch, length, body condition, feeding intensity, and growth between unmarked and hatchery fish, suggesting that both groups were responding similarly to ocean conditions. 相似文献
17.
We review studies of interactions between hatchery and wild Pacific salmon in the Russian Far East. This includes the role of hatchery practices that result in premature migration to the sea and increased mortality, and data on feeding and territorial competition between juveniles of hatchery and wild origin. In the course of downstream migration many juvenile hatchery salmon are eliminated by wild salmon predation. During the marine period, Japanese hatchery chum salmon (Oncorhynchus keta) distribution overlaps the distribution of Russian wild salmon. Consequently, replacement of wild populations by hatchery fishes, as a result of abundant juvenile hatchery releases combined with extensive poaching in spawning grounds, is apparent in some Russian rivers. Interactions between the populations occur in all habitats. The importance of conservation of wild salmon populations requires a more detailed study of the consequences of interactions between natural and artificially reared fishes. 相似文献
18.
R. J. Beamish R. M. Sweeting C. M. Neville K. L. Lange T. D. Beacham D. Preikshot 《Environmental Biology of Fishes》2012,94(1):135-148
The population dynamics of chinook salmon (Oncorhynchus tshawytscha) from the Cowichan River on Vancouver Island, British Columbia, Canada are used by the Pacific Salmon Commission as an index
of the general state of chinook salmon coast wide. In recent years the production declined to very low levels despite the
use of a hatchery that was intended to increase production by improving the number of smolts entering the ocean. In 2008,
we carried out an extensive study of the early marine survival of the hatchery and wild juvenile chinook salmon. We found
that both rearing types mostly remained within the Gulf Islands study area during the period when most of the marine mortality
occurred for the hatchery fish. By mid September, approximately 1.3% of all hatchery fish survived, compared to 7.8%–31.5%
for wild fish. This six to 24 times difference in survival could negate an estimated increased egg-to-smolt survival of about
13% that is theorized to result through the use of a hatchery. Estimates of the early marine survival are approximate, but
sufficient to show a dramatic difference in the response of the two rearing types to the marine nursery area. If the declining
trend in production continues for both rearing types, modifications to the hatchery program are needed to improve survival
or an emphasis on improving the abundances of wild stocks is necessary, or both. The discovery that the juvenile Cowichan
River chinook salmon remain within a relatively confined area of the Gulf Islands within the Strait of Georgia offers an excellent
opportunity to research the mechanisms that cause the early marine mortalities and hopefully contribute to a management that
improves the production. 相似文献
19.
Lev A. Zhivotovsky Ludmila K. Fedorova Galina A. Rubtsova Marina V. Shitova Tatiana A. Rakitskaya Valentina D. Prokhorovskaya Boris P. Smirnov Alexander M. Kaev Vladimir M. Chupakhin Vladimir G. Samarsky Victor P. Pogodin Sergey I. Borzov Konstantin I. Afanasiev 《Environmental Biology of Fishes》2012,94(1):249-258
A harvested stock of chum salmon homing to Kurilskiy Bay, Iturup Island, consists of two genetically distinct river populations that reproduce in two rivers that drain into the bay and are characterized by limited gene flow. One of these is small and can be regarded as wild, whereas the other is much larger and, until recently, was composed of naturally reproducing components spawning in the river??s mainstem and tributaries, with almost no hatchery reproduction during the past two decades. The only human impact on reproduction of the chum salmon stock was regulation of the escapement, with officially accepted limits to avoid ??over-escapement??. Recently the hatchery began to release a large amount of chum salmon juveniles. As confirmed by data on variation in both age composition and microsatellite DNA, first-generation hatchery-origin fish that returned from the first large releases occupied spawning grounds and presumably competed directly with, and potentially displaced wild fish. The most dramatic example is a genetically distinct beach-spawning form of chum salmon that was swamped by much more numerous hatchery-origin fish of the river-spawning form. In order to restore and support naturally reproduced population components, careful estimation of the carrying capacity of natural spawning grounds is necessary with efforts to increase escapement to these habitats. We also recommend concerted efforts to restore and conserve a unique beach-spawning population of chum salmon. We further recommend development of a marking program for direct estimation of straying and evaluation of ecological and genetic impacts of hatchery fish on neighboring wild and natural populations. 相似文献
20.
Plasticity of smolting in spring chinook salmon: relation to growth and insulin-like growth factor-I 总被引:1,自引:0,他引:1
In two year classes of Willamette River spring chinook salmon, reared at the Willamette Hatchery, and two groups of Yakima River spring chinook salmon, one sampled from the Yakima River and the other reared in a hatchery, fish which had relatively high growth rates in the summer–autumn period smolted in the autumn as measured by increases in gill Na+ K+ AT Pase activity. In contrast, groups with relatively low growth rate did not smolt in the autumn. Plasma levels of insulin-like growth factor-I (IGF-I) showed discrete differences between groups, with high levels associated with increased gill Na+ K+ AT Pase activities. These results demonstrate that smolting is plastic in spring chinook salmon, occurring in the autumn or the spring. In addition, smolting appeared to be related to growth rate; however, the relationships shown were correlational and causal mechanisms were not elucidated. Yet, the results do indicate a relationship between growth, an endocrine growth factor and smolting, suggesting a mechanistic link between developmental plasticity and the environment mediated by the endocrine system. 相似文献