The total world catch from marine and freshwater wild stocks has peaked and may be slightly declining. There appear to be few significant resources to be developed, and the majority of the world's fish stocks are intensively exploited. Many marine ecosystems have been profoundly changed by fishing and other human activities. Although most of the world's major fisheries continue to produce substantial sustainable yield, a number have been severely overfished, and many more stocks appear to be heading toward depletion. The world's fisheries continue to be heavily subsidized, which encourages overfishing and provides society with a small fraction of the potential economic benefits. In most of the world's fisheries there is a “race for fish” in which boats compete to catch the fish before a quota is achieved or the fish are caught by someone else. The race for fish leads to economic inefficiency, poor quality product, and pressure to extract every fish for short-term gain. A number of countries have instituted alternative management practices that eliminate the race for fish and encourage economic efficiency, use lower exploitation rates that deliberately do not attempt to maximize biological yield, and encourage reduced fishing costs and increased value of products. In fisheries where this transition has taken place, we see the potential for future sustainability, but in those fisheries where the race for fish continues, we anticipate further declines in abundance, further loss of jobs and fishing communities, and potential structural change to marine ecosystems.
Snow crab (Chionoecetes opilio) migrations in the eastern Bering Sea have long been ignored. Based on preliminary information, we hypothesized that females undergo an extensive ontogenetic migration, tracking down environmental gradients. We analyzed a 25-year time series of survey data and defined ontogenetic stages in terms of a "shell condition index" calibrated with radiochemical methods. "Pseudo-cohorts" of mature females (groups of females that undergo puberty molt in a given year) "recruit" to the mature female pool in the Middle Domain (50100 m) of the intermediate shelf. Females undergo puberty molt and primiparous mating in winter. Over the next year, they migrate an average net distance of 73.5 nautical miles towards the shelf edge following a predominantly northeastsouthwest direction. Maximum post-terminal molt life span is 67 years. Results support the hypothesis that the variable tracked is near-bottom temperature. Although near-bottom temperature fields vary from year to year, the corresponding vector field is a conservative template, which explains the consistency observed in the pattern of migration. Elucidation of the life history schedule of mature female snow crabs in the eastern Bering Sea revealed that it is very similar to that reported for eastern Canada, although patterns of migration may differ substantially between the two systems.
Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio‐temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate‐driven ocean changes.
ABSTRACT' Newly settled individuals and juveniles of several benthic decapod crustaceans spend their first months or years in nursery habitats different from those of the adult population. It was unknown if this was the case for the squat lobster Pleuroncodes monodon, an exploited crustacean which inhabits the continental shelf off central Chile, and of which 2 adult populations exist, the larger Achira (35' 10' S to 36' 15' S) and the smaller Biobio (36' 35' S to 36' 50' S). We report here the presence of a large nursery area of the species, connecting both adult populations; the habitat is dominated by extensive sulphide microbial communities which fluorish at very low oxygen concentrations. We inferred the existence of northerly and southerly migration routes from the nursery ground to the adult populations, with juvenile year classes migrating as they advance through age classes. The juvenile population was composed of 2 year classes: 0 yr old (newly settled mdividuals) and 1 yr old juveniles; thus juveniles seemed to spend their first year of life in the nursery area. Total abundance was estimated as 3290 x lo6 individuals (asymmetric 95 % confidence interval: 2153 to 7039 x lo6), although the above figure is a lower bound because the sampling did not cover the whole nursery area. We hypothesize that the Biobio adult population is not self-sustaining, but depends on a surplus production of juveniles from the Achira population.
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