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1.
Marine fisheries as ecological experiments 总被引:1,自引:0,他引:1
There are many examples of ecological theory informing fishery management. Yet fisheries also provide tremendous opportunities
to test ecological theory through large-scale, repeated, and well-documented perturbations of natural systems. Although treating
fisheries as experiments presents several challenges, few comparable tests exist at the ecosystem scale. Experimental manipulations
of fish populations in lakes have been widely used to develop and test ecological theory. Controlled manipulation of fish
populations in open marine systems is rarely possible, but fisheries data provide a valuable substitute for such manipulations.
To highlight the value of marine fisheries data, we review leading ecological theories that have been empirically tested using
such data. For example, density dependence has been examined through meta-analysis of spawning stock and recruitment data
to show that compensation (higher population growth) occurs commonly when populations are reduced to low levels, while depensation
(the Allee effect) is rare. As populations decline, spatial changes typically involve populations contracting into high-density
core habitats while abandoning less productive habitats. Fishing down predators may result in trophic cascades, possibly shifting
entire ecosystems into alternate stable states, although alternate states can be maintained by both ecological processes and
continued fishing pressure. Conversely, depleting low trophic level groups may affect central-place foragers, although these
bottom–up effects rarely appear to impact fish—perhaps because many fish populations have been reduced to the point that they
are no longer prey limited. Fisheries provide empirical tests for diversity–stability relations: catch data suggest that more
diverse systems recover faster and provide more stable returns than less diverse systems. Fisheries have also provided examples
of the tragedy of the commons, as well as counter-examples where common property resources have been managed successfully.
We also address two barriers to use of fisheries data to answer ecological questions: differences in terminology for similar
concepts and misuse of records of fishery landings (catch data) as a proxy for biomass trends. 相似文献
2.
Sara Bonanomi Nina Overgaard Therkildsen Anja Retzel Rasmus Berg Hedeholm Martin Wæver Pedersen Dorte Meldrup Christophe Pampoulie Jakob Hemmer‐Hansen Peter Grønkjær Einar Eg Nielsen 《Molecular ecology》2016,25(12):2727-2734
The occurrence of natal homing in marine fish remains a fundamental question in fish ecology as its unequivocal demonstration requires tracking of individuals from fertilization to reproduction. Here, we provide evidence of long‐distance natal homing (>1000 km) over more than 60 years in Atlantic cod (Gadus morhua), through genetic analysis of archived samples from marked and recaptured individuals. Using a high differentiation single‐nucleotide polymorphism assay, we demonstrate that the vast majority of cod tagged in West Greenland and recaptured on Icelandic spawning grounds belonged to the Iceland offshore population, strongly supporting a hypothesis of homing. The high degree of natal fidelity observed provides the evolutionary settings for development of locally adapted populations in marine fish and emphasize the need to consider portfolio effects in marine fisheries management strategies. 相似文献
3.
Martin Krko?ek Crawford W. Revie Patrick G. Gargan Ove T. Skilbrei Bengt Finstad Christopher D. Todd 《Proceedings. Biological sciences / The Royal Society》2013,280(1750)
Parasites may have large effects on host population dynamics, marine fisheries and conservation, but a clear elucidation of their impact is limited by a lack of ecosystem-scale experimental data. We conducted a meta-analysis of replicated manipulative field experiments concerning the influence of parasitism by crustaceans on the marine survival of Atlantic salmon (Salmo salar L.). The data include 24 trials in which tagged smolts (totalling 283 347 fish; 1996–2008) were released as paired control and parasiticide-treated groups into 10 areas of Ireland and Norway. All experimental fish were infection-free when released into freshwater, and a proportion of each group was recovered as adult recruits returning to coastal waters 1 or more years later. Treatment had a significant positive effect on survival to recruitment, with an overall effect size (odds ratio) of 1.29 that corresponds to an estimated loss of 39 per cent (95% CI: 18–55%) of adult salmon recruitment. The parasitic crustaceans were probably acquired during early marine migration in areas that host large aquaculture populations of domesticated salmon, which elevate local abundances of ectoparasitic copepods—particularly Lepeophtheirus salmonis. These results provide experimental evidence from a large marine ecosystem that parasites can have large impacts on fish recruitment, fisheries and conservation. 相似文献
4.
Density dependence,prey accessibility and prey depletion by fisheries drive Peruvian seabird population dynamics 下载免费PDF全文
Christophe Barbraud Arnaud Bertrand Marilú Bouchón Alexis Chaigneau Karine Delord Hervé Demarcq Olivier Gimenez Mariano Gutiérrez Torero Dimitri Gutiérrez Ricardo Oliveros‐Ramos Giannina Passuni Yann Tremblay Sophie Bertrand 《Ecography》2018,41(7):1092-1102
In marine ecosystems top predator populations are shaped by environmental factors affecting their prey abundance. Coupling top predators’ population studies with independent records of prey abundance suggests that prey fluctuations affect fecundity parameters and abundance of their predators. However, prey may be abundant but inaccessible to their predators and a major challenge is to determine the relative importance of prey accessibility in shaping seabird populations. In addition, disentangling the effects of prey abundance and accessibility from the effects of prey removal by fisheries, while accounting for density dependence, remains challenging for marine top predators. Here, we investigate how climate, population density, and the accessibility and removal of prey (the Peruvian anchovy Engraulis ringens) by fisheries influence the population dynamics of the largest sedentary seabird community (≈ 4 million individuals belonging to guanay cormorant Phalacrocorax bougainvillii, Peruvian booby Sula variegata and Peruvian pelican Pelecanus thagus) of the northern Humboldt Current System over the past half‐century. Using Gompertz state–space models we found strong evidence for density dependence in abundance for the three seabird species. After accounting for density dependence, sea surface temperature, prey accessibility (defined by the depth of the upper limit of the subsurface oxygen minimum zone) and prey removal by fisheries were retained as the best predictors of annual population size across species. These factors affected seabird abundance the current year and with year lags, suggesting effects on several demographic parameters including breeding propensity and adult survival. These findings highlight the effects of prey accessibility and fishery removals on seabird populations in marine ecosystems. This will help refine management objectives of marine ecosystems in order to ensure sufficient biomass of forage fish to avoid constraining seabird population dynamics, while taking into account of the effects of environmental variability. 相似文献
5.
The world faces a global fishing crisis. Wild marine fisheries comprise nearly 15% of all animal protein in the human diet, but, according to the U.N. Food and Agriculture Organization, nearly 60% of all commercially important marine fish stocks are overexploited, recovering, or depleted (FAO 2012 ; Fig. 1 ). Some authors have suggested that the large population sizes of harvested marine fish make even collapsed populations resistant to the loss of genetic variation by genetic drift (e.g. Beverton 1990 ). In contrast, others have argued that the loss of alleles because of overfishing may actually be more dramatic in large populations than in small ones (Ryman et al. 1995). In this issue, Pinsky & Palumbi (2014) report that overfished populations have approximately 2% lower heterozygosity and 12% lower allelic richness than populations that are not overfished. They also performed simulations which suggest that their estimates likely underestimate the actual loss of rare alleles by a factor of three or four. This important paper shows that the harvesting of marine fish can have genetic effects that threaten the long‐term sustainability of this valuable resource. 相似文献
6.
M. A. Samoilys 《Coral reefs (Online)》1997,16(3):151-158
Movement by the larger more mobile species of coral reef fish plays a significant role in determining patterns in abundance
and population structure. Fish movement is also relevant to the use and effectiveness of marine reserves in managing fish
populations. Coral trout are large piscivorous serranids supporting major fisheries on the Great Barrier Reef (GBR). This
study reports on the within-reef movement of the common coral trout, Plectropomus leopardus, at Heron Reef, southern GBR, over a twelve month period, investigated by tagging and underwater tracking. Tracking of coral
trout revealed no apparent relationship between the area moved and stage of tide or time of day. However, movement areas were
affected by the size of fish: in spring a linear relationship between fish size and area of movement was measured, but in
summer the largest (male) fish moved over significantly smaller areas than medium-sized fish. Movement of males may be related
to cleaning behaviour and spawning. Fifty nine percent (n=101) of the tagged fish were resighted over periods of 4–5 months, in “home sites” measuring ∼2000 m2. Coral trout were not restricted to home sites, but moved on average 2 km along the reef slope; maximum distances of 7–7.5 km
were measured. Coral trout appear to range as mobile, opportunistic predators, but also maintain home sites for access to
shelter and cleaning stations.
Accepted: 1 August 1996 相似文献
7.
《Anthrozo?s》2013,26(1):20-30
ABSTRACTPublic attitudes toward the use of fisheries and marine mammals in the northwest Atlantic have played an influential role in recent controversies over management of these resources. A thorough assessment of public sentiment has, however, been lacking. We describe the results of a survey conducted to assess Canadian public opinion regarding a variety of commercial fisheries and marine mammal issues. Over one thousand, randomly selected adult Canadians were surveyed concerning their attitudes, knowledge, and concerns toward the conservation and management of marine mammals in the northwest Atlantic. The sample included 875 members of the general public, 130 sealers and 81 commercial fishermen.Most Canadians (93–95%) in all sampling groups and in all provinces, except Quebec (54%), expressed concern about conflicts between marine mammals and commercial fisheries. Knowledge of basic marine mammal biology, however, was strikingly deficient and variable among groups: sealers obtained the highest knowledge rating, fishers were intermediate, and the general public scored lowest. The views of the Canadian general public, sealers, and commercial fishers were highly divergent regarding prioritization of goals for Canada's commercial fishing industry. Sealers and fishers emphasized employment, cultural and economic considerations, while the general public placed greater emphasis on ecological and ethical matters. All groups agreed that the most significant threats to Canada's commercial fisheries included fishing by foreign countries, pollution, and over-fishing. Competition from marine mammals and damage to fishing equipment by marine mammals were rated as the least important threats. Fishing by foreign vessels in Canadian waters was regarded by all groups with particular suspicion.Unlike sealers and fishers, the general public consistently disputed the notion of sacrificing the needs of marine mammals for the benefit of commercial fishing. The public also expressed a strong preference for including fishing impacts on marine mammals in setting allowable catch quotas for commercial fish stocks, and further indicated a willingness to favor the interests of marine mammals over commercial fisheries in marine mammal entanglement situations.More than ninety percent of all respondents indicated strong support for the ‘existence value’ of seals. Most Canadians opposed sealing for fur, whereas most approved of harvesting abundant adult seal populations for meat, harvests associated with the cultures of native peoples, and harvests important to local economies. Respondents were divided regarding the harvest of seals that damage fishing gear. All groups strongly opposed the harvest of newborn seals. Sealers and residents of Newfoundland supported lethal methods of seal population control, while residents of large urban areas and women were inclined to approve of non-lethal measures. An overwhelming majority of Canadians objected to the use of poisons or clubs as a means of population control.Consideration of the results of this study could provide an enhanced basis for fashioning mutually acceptable policy solutions and mitigating conflicts between commercial fisheries and marine mammal conservation in the northwest Atlantic Ocean. 相似文献
8.
The histories of management of the Sumilon and Apo marine reserves in the Philippines provide a stark contrast. Both began
with marine conservation and education programs at the community level, initiated by the Marine Laboratory of Silliman University
in 1973 at Sumilon, and in 1976 at Apo. At both islands community support for the “no take” reserve concept evolved gradually,
via perceived benefits of increased local fish yields and income from tourism. However, Sumilon reserve has been fished down
twice (in 1984,1992), and was still being fished in December 1998. Apo reserve has been protected from fishing successfully
for 16 y (1982–1998). The management histories of these two marine reserves are the longest and most detailed available for
coral reefs. Scientific data spanning 1976–1993 for Sumilon and 1980–1993 for Apo have provided some of the best available
evidence of the utility of such reserves as management tools in coral reef fisheries. At Sumilon, collapse of reserve protection
in 1984, after 9.5 y of restrictions on fishing, led to significant declines in reef fisheries yields in areas adjacent to
the reserve. At Apo, continuous protection from 1982 to 1993 has led to consistent build up of fish in the reserve and some
evidence that local fish yields have increased. The unique time series of scientific data obtained from Sumilon and Apo islands
are the result of their distinct management histories. The greater success of management at Apo was due to community support
for the reserve concept being actively maintained for the past 16 y. Socio-political factors caused the level of community
support for the Sumilon reserve to wax and wane over this period. Both case histories have had a profound effect on marine
resource management in the Philippines. As marine reserve models they had substantial influence on the design of the National
Integrated Protected Area System (NIPAS). Policy now encourages co-management between the National government and local communities,
with a strong emphasis on decentralization of decision making and recognition of local territorial use rights in fisheries.
Accepted: 14 May 1999 相似文献
9.
TRISTAN ROUYER GEIR OTTERSEN JOËL M. DURANT MANUEL HIDALGO DAG Ø. HJERMANN JONAS PERSSON LEIF CHR. STIGE NILS CHR. STENSETH 《Global Change Biology》2011,17(10):3046-3057
Accumulating evidence shows that environmental fluctuations and exploitation jointly affect marine fish populations, and understanding their interaction is a key issue for fisheries ecology. In particular, it has been proposed that age truncation induced by fisheries exploitation may increase the population's sensitivity to climate. In this study, we use unique long‐term abundance data for the Northeast Arctic stock of cod (Gadus morhua) and the Norwegian Spring‐Spawning stock of herring (Clupea harengus), which we analyze using techniques based on age‐structured population matrices. After identifying time periods with different age distributions in the spawning stock, we use linear models to quantify the relative effect of exploitation and temperature on the population growth rates. For the two populations, age truncation was found to be associated with an increasing importance of temperature and a relatively decreasing importance of exploitation, while the population growth rate became increasingly sensitive to recruitment variations. The results suggested that the removal of older age classes reduced the buffering capacity of the population, thereby making the population growth rate more dependent on recruitment than adult survival and increasing the effect of environmental fluctuations. Age structure appeared as a key characteristic that can affect the response of fish stocks to climate variations and its consequences may be of key importance for conservation and management. 相似文献
10.
Maladaptive changes in multiple traits caused by fishing: impediments to population recovery 总被引:2,自引:0,他引:2
Some overharvested fish populations fail to recover even after considerable reductions in fishing pressure. The reasons are unclear but may involve genetic changes in life history traits that are detrimental to population growth when natural environmental factors prevail. We empirically modelled this process by subjecting populations of a harvested marine fish, the Atlantic silverside, to experimental size-biased fishing regimes over five generations and then measured correlated responses across multiple traits. Populations where large fish were selectively harvested (as in most fisheries) displayed substantial declines in fecundity, egg volume, larval size at hatch, larval viability, larval growth rates, food consumption rate and conversion efficiency, vertebral number, and willingness to forage. These genetically based changes in numerous traits generally reduce the capacity for population recovery. 相似文献
11.
Protection from fishing generally results in an increase in the abundance and biomass of species targeted by fisheries within
marine reserve boundaries. Natural refuges such as depth may also protect such species, yet few studies in the Indo Pacific
have investigated the effects of depth concomitant with marine reserves. We studied the effects of artisanal fishing and depth
on reef fish assemblages in the Kubulau District of Vanua Levu Island, Fiji, using baited remote underwater stereo-video systems.
Video samples were collected from shallow (5–8 m) and deep (25–30 m) sites inside and outside of a large old marine reserve
(60.6 km2, 13 years old) and a small new marine reserve (4.25 km2, 4 years old). Species richness tended to be greater in the shallow waters of the large old reserve when compared to fished
areas. In the deeper waters, species richness appeared to be comparable. The difference in shallow waters was driven by species
targeted by fisheries, indicative of a depth refuge effect. In contrast, differences in the abundance composition of the fish
assemblage existed between protected and fished areas for deep sites, but not shallow. Fish species targeted by local fisheries
were 89% more abundant inside the large old reserve than surrounding fished areas, while non-targeted species were comparable.
We observed no difference in the species richness or abundance of species targeted by fisheries inside and outside of the
small new reserve. This study suggests that artisanal fishing impacts on the abundance and species richness of coral reef
fish assemblages and effects of protection are more apparent with large reserves that have been established for a long period
of time. Observed effects of protection also vary with depth, highlighting the importance of explicitly incorporating multiple
depth strata in studies of marine reserves. 相似文献
12.
The red drums, Sciaenops ocellatus, are predatory marine fish from Atlantic American coast. They were introduced to Taiwan for aquaculture purpose in 1987 and
have been reported in the wild along the southwest coast of Taiwan since 1998. Their current distribution is on the western
coast of Taiwan and the Matsu Islands of Fujian Province where there are sand and mud bottoms. However, the discontinuous
populations of Taiwan and Matsu indicated different sources of introduction. The facts that there are consecutive records
of red drums for 7 years including every single month, at multiple localities, and the fish’s larger size all point to their
survival in the wild. The mechanisms of their introductions are probably the escapes from net cages as well as the deliberate
releases to improve fisheries and for religious activities. This paper documents for the first time a marine fish has invaded
and established in coastal water off western Taiwan and the Indo-West Pacific. The ecological impact of red drums on the local
fish community is still unknown and calls for further studies. 相似文献
13.
Richard C. Hoffmann 《Helgoland Marine Research》2005,59(1):22-30
Humans have exploited European aquatic resources since at least the Palaeolithic, but during the Middle Ages rising human populations and demand initiated great changes in many fisheries. To help understand the past and present of the Wadden Sea, this paper sets the main developments of medieval fisheries in the context of changing larger European social and aquatic environments ca. 500–1500 A.D. Anthropogenic influences on fish populations and aquatic habitats interacted with natural environmental variations. Both nutritional and cultural needs shaped human consumption of aquatic organisms. Many fisheries met the demand for food by economic reorientation from subsistence to artisanal and then even fully commercial purposes. Exploitation slowly shifted from limited or deteriorating local inland and inshore fish populations to frontier, commonly marine, and increasingly pelagic resources. Some inland regions developed aquaculture to enhance local supplies of fresh fish. General processes are illustrated by case studies of selected indicator species from freshwater and marine habitats generally pertinent to the region surrounding the Wadden Sea. Anadromous salmon (Salmo salar) and sturgeon (Acipenser sturio) were negatively affected by overfishing and by unintentional human alteration of critical habitat. Habitat preferences of catadromous eel (Anguilla anguilla) and exotic carp (Cyprinus carpio) let these species gain from medieval human activities. In the case of herring (Clupea harengus), Europes largest early commercial marine fishery, technological innovations which raised production and consumption played off against long-term consequences of intensely exploiting sensitive natural systems. 相似文献
14.
Understanding patterns of connectivity among marine fish populations with demersal adults and pelagic larvae is critical for
effective conservation of west coast rockfishes. The brown rockfish (Sebastes auriculatus) occurs in nearshore habitat and is common from northern Baja California, Mexico to northern California, rare off the outer
coast of Oregon and Washington and again common in the inland waters of Puget Sound, Washington. Here we examine patterns
of microsatellite DNA diversity from throughout the species’ range as an indirect measure of long-term trends in larval dispersal.
Genetic divergence was large and highly significant over all populations (F
ST=0.056, P<0.0001), and was significantly correlated with geographic distance when considering coastal populations. The best estimates
of mean coastal dispersal distance were on the order of 10 km or less per generation. Diversity was relatively low in the
Puget Sound, suggesting that Puget Sound rockfish populations experienced a post-glacial founder effect followed by genetic
isolation and low effective population size. Puget Sound individuals appeared to have recent mixed ancestry as a result of
introgression with S. maliger and S. caurinus. Genetic isolation of Puget Sound fish provides a basis for consideration as a Distinct Population Segment (DPS) under the
provisions of the Endangered Species Act. We recommend that coastal brown rockfish fisheries be managed at regional rather
than coast-wide scales, and that design of marine reserve networks considers the surprisingly low realized dispersal distance
of some species with high dispersal potential. 相似文献
15.
This review is based on 58 climate-fisheries models published over the last 28 years that describe the impacts of fishery
pressure and environmental variability on populations and ecosystems and include basic principles of population dynamics.
It points out that the incorporation of environmental factors in fishery models has already been done and is of great importance
for future models used in the assessment of marine resources. The work is guided by the questions to what extent have these
models a) enhanced our understanding of the interrelationships between the environment, the fishery and the state of the exploited
resources and b) helped to improve the prediction of population dynamics and the assessment of marine resources. For each
of the six most commonly used model categories a case study is critically analyzed. The problems of “breaking relationships”
between environmental factors and the biological response used in models, the trade-off between model complexity (realism)
and simplicity (data availability) and the potential of multivariate climate indices for forecasting ecosystem states and
for use as proxies for combined models are discussed, as are novel non-linear and spatially explicit modeling approaches.
Approaches differ in terms of model complexity, use of linear or non-linear equations, number of parameters, forecast time
horizon and type of resource modelled. A majority of the models were constructed for fish and invertebrate stocks of the northeast
Pacific and the epicontinental seas of the Atlantic, reflecting the advancement of fisheries science in these regions. New,
in parts highly complex models and sophisticated approaches were identified. The reviewed studies demonstrate that the performance
of fished stocks can better be described if environmental or climatic variability is incorporated into the fisheries models.
We conclude that due to the already available knowledge, the greatly enhanced computer power, new methods and recent findings
of large-scale climatic/oceanographic cycles, fisheries modeling should progress greatly in the coming years. 相似文献
16.
Genetic variation among populations of the Antarctic toothfish: evolutionary insights and implications for conservation 总被引:1,自引:1,他引:0
Commercial fishing is having an increasingly negative impact on marine biodiversity, with over 70% of the world's fish stocks being fully exploited and, in many cases, overexploited. On top of this, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has granted commercial fishing permits in the most remote marine environment on earth, the high-latitude Southern Ocean. The primary target of these new commercial fishing ventures is the large pelagic piscivorous predator, the Antarctic toothfish (Dissostichus mawsoni). Unfortunately, little information is available on the demography, genetics, or life history of this large fish. Without such information we have little idea as to the effects of commercial fishing on the population structure and survival of this species. In this study, we focus on patterns of genetic diversity within and between geographically disparate populations of the Antarctic toothfish, using randomly amplified polymorphic DNA markers. Results of our study showed high levels of genetic similarity within and between populations. Despite high levels of genetic similarity, genetic analyses detected significant population structure, including fixed differences among populations, a significant fixation index (Fst) and between-population differentiation via a Mantel test. From a conservation perspective, low levels of genetic diversity may be indicative of relatively small populations that would not be able to withstand heavy commercial fishing pressures. Given that there is evidence for significant genetic structure, it will be important to manage these fisheries in a manner that will help prevent the loss of unique genetic variation from regional overfishing. 相似文献
17.
Steven J. Cooke William M. Twardek Andrea J. Reid Robert J. Lennox Sascha C. Danylchuk Jacob W. Brownscombe Shannon D. Bower Robert Arlinghaus Kieran Hyder Andy J. Danylchuk 《Journal of fish biology》2019,94(6):845-856
Recreational fisheries that use rod and reel (i.e., angling) operate around the globe in diverse freshwater and marine habitats, targeting many different gamefish species and engaging at least 220 million participants. The motivations for fishing vary extensively; whether anglers engage in catch-and-release or are harvest-oriented, there is strong potential for recreational fisheries to be conducted in a manner that is both responsible and sustainable. There are many examples of recreational fisheries that are well-managed where anglers, the angling industry and managers engage in responsible behaviours that both contribute to long-term sustainability of fish populations and the sector. Yet, recreational fisheries do not operate in a vacuum; fish populations face threats and stressors including harvest from other sectors as well as environmental change, a defining characteristic of the Anthropocene. We argue that the future of recreational fisheries and indeed many wild fish populations and aquatic ecosystems depends on having responsible and sustainable (R&S) recreational fisheries whilst, where possible, addressing, or at least lobbying for increased awareness about the threats to recreational fisheries emanating from outside the sector (e.g., climate change). Here, we first consider how the concepts of R&S intersect in the recreational fishing sector in an increasingly complex socio-cultural context. Next, we explore the role of the angler, angling industry and decision-makers in achieving R&S fisheries. We extend this idea further by considering the consequences of a future without recreational fisheries (either because of failures related to R&S) and explore a pertinent case study situated in Uttarakahand, India. Unlike other fisheries sectors where the number of participants is relatively small, recreational angling participants are numerous and widespread, such that if their actions are responsible, they have the potential to be a key voice for conservation and serve as a major force for good in the Anthropocene. What remains to be seen is whether this will be achieved, or if failure will occur to the point that recreational fisheries face increasing pressure to cease, as a result of external environmental threats, the environmental effects of recreational fishing and emerging ethical concerns about the welfare of angled fish. 相似文献
18.
R. T. Graham R. Carcamo K. L. Rhodes C. M. Roberts N. Requena 《Coral reefs (Online)》2008,27(2):311-319
Scientific information on reef fish spawning aggregation fisheries is sparse in light of numerous regional declines and extirpations
from overexploitation. Fisher interviews of the small-scale commercial mutton snapper (Lutjanus analis) spawning aggregation fishery at Gladden Spit, Belize, suggests a historic decadal decline. The reported trend is supported
by analysis of inter-seasonal catch and effort and yield (2000–2002) that reveals a 59% decline in catch per unit effort (CPUE)
and a 22% decrease in mean landings per boat. Declining population-level trends are also supported by a significant decrease
in inter-annual median lengths of mutton snappers (2000–2006). These findings demonstrate the need for additional life history
information that includes length-associated age and details on growth to provide clearer support of the effects on, and responses
by, populations following fishing. In view of the historical changes to mutton snapper CPUE and landings at Gladden Spit and
the fishery-associated declines in fish spawning aggregations observed globally, a precautionary approach to spawning aggregation
management is warranted that provides full protection from fishing to enhance population persistence. The findings also highlight
the need for substantially greater enforcement and long-term fisheries monitoring under a comprehensive regional management
strategy. 相似文献
19.
The frequently observed positive relationship between fish population abundance and spatial distribution suggests that changes in distribution can be indicative of trends in abundance. If contractions in spatial distribution precede declines in spawning stock biomass (SSB), spatial distribution reference points could complement the SSB reference points that are commonly used in marine conservation biology and fisheries management. When relevant spatial distribution information is integrated into fisheries management and recovery plans, risks and uncertainties associated with a plan based solely on the SSB criterion would be reduced. To assess the added value of spatial distribution data, we examine the relationship between SSB and four metrics of spatial distribution intended to reflect changes in population range, concentration, and density for 10 demersal populations (9 species) inhabiting the Scotian Shelf, Northwest Atlantic. Our primary purpose is to assess their potential to serve as indices of SSB, using fisheries independent survey data. We find that metrics of density offer the best correlate of spawner biomass. A decline in the frequency of encountering high density areas is associated with, and in a few cases preceded by, rapid declines in SSB in 6 of 10 populations. Density-based indices have considerable potential to serve both as an indicator of SSB and as spatially based reference points in fisheries management. 相似文献
20.
Status of research on Yangtze fish biology and fisheries 总被引:2,自引:0,他引:2
The Yangtze is the largest river in China and the third largest river in the world. Being pregnant with plentiful fish resources,
it is not only the representative of the areas with biological diversity, but also a cradle of freshwater fisheries in China.
In the Yangtze, at present, the fishery resources are seriously depleted; the fishery yield by fishing is significantly reduced;
significant changes have occurred on the structure of fish community, with decrease in migratory fish species, reduction in
the quantity of the populations of rare, peculiar and economically important fish species and increase in the number of exotic
fish species, and severe trend in fish stunting. Habitat fragmentation and shrinkage, resources overexploitation, water pollution
and invasion of exotic species are the main causes for threatening fish stocks in the Yangtze River. Since 1950’s, a lot of
scientific researches have been conducted on biology of fishes from the Yangtze River and its fisheries to provide scientific
basis for their protection. In recent years, measures such as closed spring, fish reserves, artificial enhancement & release,
ecological rehabilitation, fishery management and international cooperation have played important roles. Nevertheless, researches
on fishes from the Yangtze cannot adequately meet the demand for their protection. Especially, those in the aspects of population
ecology of Yangtze fishes, species endangerment mechanism, ecological effects of large hydraulic projects and protection strategy
are not deep enough. It is recommended that scientific researches should be conducted in comprehensive survey of Yangtze fish
resources, fish endangerment mechanism, techniques in artificial enhancement and release of key species, risk assessment of
exotic species, ecological rehabilitation of major fisheries functional zones, etc. 相似文献