Quantifying overlap between the Deepwater Horizon oil spill and predicted bluefin tuna spawning habitat in the Gulf of Mexico

Atlantic bluefin tuna (Thunnus thynnus) are distributed throughout the North Atlantic and are both economically valuable and heavily exploited. The fishery is currently managed as two spawning populations, with the GOM population being severely depleted for over 20 years. In April-August of 2010, the Deepwater Horizon oil spill released approximately 4 million barrels of oil into the GOM, with severe ecosystem and economic impacts. Acute oil exposure results in mortality of bluefin eggs and larvae, while chronic effects on spawning adults are less well understood. Here we used 16 years of electronic tagging data for 66 bluefin tuna to identify spawning events, to quantify habitat preferences, and to predict habitat use and oil exposure within Gulf of Mexico spawning grounds. More than 54,000 km(2) (5%) of predicted spawning habitat within the US EEZ was oiled during the week of peak oil dispersal, with potentially lethal effects on eggs and larvae. Although the oil spill overlapped with a relatively small portion of predicted spawning habitat, the cumulative impact from oil, ocean warming and bycatch mortality on GOM spawning grounds may result in significant effects for a population that shows little evidence of rebuilding

Diel variation in fish assemblages in tidal creeks in southern Brazil

Tidal creeks are strongly influenced by tides and are therefore exposed to large differences in salinity and depth daily. Here we compare fish assemblages in tidal creeks between day and night in two tidal creeks in southern Brazil. Monthly day and night, simultaneous collections were carried out in both creeks using fyke nets. Clupeiformes tended to be caught more during the day. Cathorops spixii, Genidens genidens and Rypticus randalli tended to be caught at night. Sciaenidae also tended to be caught more during the night. In general, pelagic species were diurnal, while deep water species were nocturnal. These trends are probably due to a variety of causes, such as phylogeny, predation and net avoidance

Seagrasses, fish and fisheries

Seagrass meadows have extremely high primary and secondary productivity and support a great abundance and diversity of fish and invertebrates. A number of commercially and recreationally important species (including both fish and invertebrates) have been linked to seagrass at some stage of their life cycle, although few such species use seagrass throughout their life. Non-commercial species within seagrass may be an important food source for commercial species (forming trophic linkages). In addition, some species that do not inhabit seagrass may derive benefit from seagrass by way of exported seagrass detritus or resident/transient species that move out of seagrass (some of these topics are dealt with elsewhere in this volume: e.g. Heck and Orth, Chapter 22, Kenworthy et al., Chapter 25 and Bell et al., Chapter 26). © 2006/2007 Springer. All Rights Reserved.http://trove.nla.gov.au/work/1348907