No abstract

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The direct and indirect effects of climate change can affect, and are mediated by, changes in animal behaviour. However, we often lack sufficient empirical data to assess how large‐scale disturbances affect the behaviour of individuals, which scales up to influence communities. Here, we investigate these patterns by focusing on the foraging behaviour of butterflyfishes, prominent coral‐feeding fishes on coral reefs, before and after a mass coral bleaching event in Iriomote, Japan. In response to 65% coral mortality, coral‐feeding fishes broadened their diets, showing a significant weakening of dietary preferences across species. Multiple species reduced their consumption of bleaching‐sensitive Acropora corals, while expanding their diets to consume a variety of other coral genera. This resulted in decreased dietary overlap among butterflyfishes. Behavioural changes in response to bleaching may increase resilience of coral reef fishes in the short term. However, coral mortality has reduced populations of coral‐feeders world‐wide, indicating the changes in feeding behaviour we document here may not be sufficient to ensure long‐term resilience of butterflyfishes on coral reefs.

Despite the need to quantify total catch to support sustainable fisheries management, estimating harvests of recreational fishers remains a challenge. Harvest estimates from mark–recapture studies have proven valuable, yet animal movements and migrations may bias some of these estimates. To improve recreational harvest estimates, explore seasonal and spatial harvest patterns, and understand the influence of animal movement on exploitation rates, we conducted a mark–recapture experiment for the blue crab (Callinectes sapidus) fishery in Maryland waters of Chesapeake Bay, USA. Data were analyzed with standard tag-return methods and with revised equations that accounted for crab movement between reporting areas. Using standard calculations, state-wide recreational harvest was estimated to be 4.04 million crabs. When movement was included in the calculations, the estimate was 5.39 million, an increase of 34%. With crab movement, recreational harvest in Maryland was estimated to be 6.5% of commercial harvest, a finding consistent with previous effort surveys. The new methods presented herein are broadly applicable for estimating recreational harvest in fisheries that target mobile species and for which spatial variation in commercial harvest is known.