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.

No abstract

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...

No abstract

No abstract

Generating age estimates for long-lived fish requires particular attention to validation because they are usually difficult to age owing to narrow increment structure. A robust validation of the accuracy and precision of banded morwong, Cheilodactylus spectabilis, sampled from Tasmanian waters, was undertaken. Age at the first enumerated increment was established from analysis of juvenile cohorts, and the timing and periodicity of increment formation was established using a quantitative model from oxytetracycline (OTC) mark-recaptures at liberty for periods of up to 8 years. The accuracy of age estimates was examined independently by comparing radiocarbon values in the otolith region corresponding to the first year of growth against the south-western Pacific calibration curve. C. spectabilis is very long-lived, with males and females living to over 90 years of age. Growth modelling revealed a fast initial growth phase, terminating in an abrupt plateau near the asymptotic length. This species displays substantial sexual dimorphism in growth, with males growing to larger sizes than females.

No abstract

Seasonal variation in catchability of the southern rock lobster Jasus edwardsii, was estimated in a scientific reserve in south-east Tasmania by comparing estimates of lobster density based on direct visual observations underwater with concomitant estimates from trapping surveys. Underwater density estimates of undersized and legal-sized male and female lobsters >80 mm carapace length, did not change significantly over the 14-month study period, with the exception of undersized males (≤110 mm carapace length). Sex ratios remained constant at approximately 1 : 1. In marked contrast, catch rates of males and females and the sex ratio of trapped lobsters varied strongly with season, implying that catchability varies seasonally and with sex. Catchability of males and females was highest in early summer and lowest in winter. Impact of capture on subsequent catchability appeared to be weak, since the ratios of tagged animals in the population observed underwater generally reflected recapture rates of tagged animals in trap catches. Recapture rates increased with size and were higher for medium-sized and large males than for similar-sized females. However, for each particular sex-size group, recapture rates remained relatively constant throughout the study period.