Antarctic and Southern Ocean (ASO) marine ecosystems have been changing for at least the last 30 years, including in response to increasing ocean temperatures and changes in the extent and seasonality of sea ice; the magnitude and direction of these changes differ between regions around Antarctica that could see populations of the same species changing differently in different regions. This article reviews current and expected changes in ASO physical habitats in response to climate change. It then reviews how these changes may impact the autecology of marine biota of this polar region: microbes, zooplankton, salps, Antarctic krill, fish, cephalopods, marine mammals, seabirds, and benthos. The general prognosis for ASO marine habitats is for an overall warming and freshening, strengthening of westerly winds, with a potential pole-ward movement of those winds and the frontal systems, and an increase in ocean eddy activity. Many habitat parameters will have regionally specific changes, particularly relating to sea ice characteristics and seasonal dynamics. Lower trophic levels are expected to move south as the ocean conditions in which they are currently found move pole-ward. For Antarctic krill and finfish, the latitudinal breadth of their range will depend on their tolerance of warming oceans and changes to productivity. Ocean acidification is a concern not only for calcifying organisms but also for crustaceans such as Antarctic krill; it is also likely to be the most important change in benthic habitats over the coming century. For marine mammals and birds, the expected changes primarily relate to their flexibility in moving to alternative locations for food and the energetic cost of longer or more complex foraging trips for those that are bound to breeding colonies. Few species are sufficiently well studied to make comprehensive species-specific vulnerability assessments possible. Priorities for future work are discussed.
The sustainable mitigation of human-wildlife conflicts has become a major societal and environmental challenge globally. Among these conflicts, large marine predators feeding on fisheries catches, a behaviour termed "depredation," has emerged concomitantly with the expansion of the world's fisheries. Depredation poses threats to both the socioeconomic viability of fisheries and species conservation, stressing the need for mitigation. This review synthesizes the extent and socio-ecological impacts of depredation by sharks and marine mammals across the world, and the
Although three species of the genus Macrourus are recognized in the Southern Ocean, DNA sequencing of the mitochondrial COI gene revealed four well-supported clades. These barcode data suggest the presence of an undescribed species, a conclusion supported by meristic and morphometric examination of specimens.
The apparently intense selective differentials imposed by many fisheries may drive the rapid evolution of growth rates. In a widely-cited laboratory experiment, Conover & Munch (2002; Science 297:94-96) found considerable evolutionary change in the size of harvested fish over 4 generations. Their empirical model has since been used to estimate the impact of fishery-driven evolution on fishery sustainability. Using a mathematical, individual-based model (IBM) that simulates that experiment, we showed that the selection imposed in the Conover & Munch (2002) model is unrealistically strong when compared to harvest rates in wild fisheries. We inferred the evolutionary change that could be expected over the timescale used by Conover & Munch (2002), had they simulated more realistic harvest regimes, and found that the magnitude in their original experiment was 2.5 to 5 times greater. However, over evolutionary timescales of 30 generations and with realistic fishing pressure, the results of Conover & Munch (2002) are comparable to wild fisheries. This simulation result provides support for the use of empirical models to predict the impacts of fishery-driven evolution on yields and sustainability. Future models should consider the timing of fishing events, the trade-off between size, maturation and growth, and density-dependent effects for a comprehensive analysis of the consequences of fishery-driven evolution.KEY WORDS: Fishery-driven evolution · Evolution · Fisheries · Heritability · Life history · Selection · Individual-based model Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 369: [257][258][259][260][261][262][263][264][265][266] 2008 to genetic variation, the selective strength of fishing, and appropriate timescales. The genetically controlled proportion of life history traits is probably moderate, estimated at 0.2 to 0.3 for fish (Law 2000, Stokes & Law 2000. The selective pressure exerted by different fisheries is variable and depends upon the harvest rate and the degree to which the fishery targets particular components of the population. Gillnets can be highly size selective (Sinclair et al. 2002), and focussing fishing effort on particular fish life history stages, such as the spawning aggregations, can also exert strong selective pressures for delayed maturity (Law & Grey 1989). Given these factors, fishery-driven evolution is highly likely in fish stocks that have been fished for tens to hundreds of generations. A review of empirical studies of fishery-driven evolution suggests that, in heavily fished populations, a 25% evolutionary change in life-history traits over 30 to 40 generations is possible (Jørgensen et al. 2007).The gradual nature of evolutionary trends, as well as confounding environmental factors such as densitydependent growth compensation, impede the detection of life-history evolution in wild fisheries. A number of studies, using a variety of methods, have tried to separate environmental from genetic effects in wild fisherie...
AimQuantifying biological assemblages and their environment is a fundamental, yet statistically challenging task in conservation ecology. Here, we use a recently developed approach called Regions of Common Profile (RCP) to quantify and map the distribution of demersal fish assemblages in an ecologically significant region of the Southern Ocean to (1) gain ecological and management insights and (2) evaluate the utility of the new method for ecoregionalization.LocationNorthern Kerguelen Plateau, Subantarctic Islands, Southern Ocean.MethodsThe RCP approach is a multispecies, model‐based approach that can overcome many limitations of traditional distance‐based approaches. It simultaneously groups sites with a similar composition of species and describes the patterns of variation in assemblages using environmental data, allowing the prediction of assemblages across the study region. We apply RCP to a unique dataset of demersal fish occurrences across the northern Kerguelen Plateau to model and map the distribution of assemblages and examine the representativeness of the Heard Island and McDonald Island marine reserve.ResultsWe demonstrate that the RCP approach allows a direct and quantitative interpretation of the composition of assemblages as well as their environment. Further, the model reasonably predicts the occurrence of individual species across the plateau as well as the species composition of sites. We distinguish and map seven assemblages defined by depth, surface temperature and chlorophyll a. Shallow‐water assemblages contain a high proportion of endemic species, while deep‐water assemblages contain more cosmopolitan species. With the exception of one deep‐water assemblage, assemblages were well represented within the current Heard and McDonald Islands marine reserve.Main conclusionsThe RCP is a valuable tool for classifying biological regions with a range of ecological and conservation management applications. Our results extend current ecological and biogeographic knowledge for the northern Kerguelen Plateau, and maps of the distribution of assemblages will be useful for ongoing spatial management.
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