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Bottom trawlers land around 19 million tons of fish and invertebrates annually, almost one-quarter of wild marine landings. The extent of bottom trawling footprint (seabed area trawled at least once in a specified region and time period) is often contested but poorly described. We quantify footprints using high-resolution satellite vessel monitoring system (VMS) and logbook data on 24 continental shelves and slopes to 1,000-m depth over at least 2 years. Trawling footprint varied markedly among regions: from <10% of seabed area in Australian and New Zealand waters, the Aleutian Islands, East Bering Sea, South Chile, and Gulf of Alaska to >50% in some European seas. Overall, 14% of the 7.8 million-km2 study area was trawled, and 86% was not trawled. Trawling activity was aggregated; the most intensively trawled areas accounting for 90% of activity comprised 77% of footprint on average. Regional swept area ratio (SAR; ratio of total swept area trawled annually to total area of region, a metric of trawling intensity) and footprint area were related, providing an approach to estimate regional trawling footprints when high-resolution spatial data are unavailable. If SAR was ≤0.1, as in 8 of 24 regions, there was >95% probability that >90% of seabed was not trawled. If SAR was 7.9, equal to the highest SAR recorded, there was >95% probability that >70% of seabed was trawled. Footprints were smaller and SAR was ≤0.25 in regions where fishing rates consistently met international sustainability benchmarks for fish stocks, implying collateral environmental benefits from sustainable fishing.

Bottom trawlers land around 19 million tons of fish and invertebrates annually, almost one-quarter of wild marine landings. The extent of bottom trawling footprint (seabed area trawled at least once in a specified region and time period) is often contested but poorly described. We quantify footprints using high-resolution satellite vessel monitoring system (VMS) and logbook data on 24 continental shelves and slopes to 1,000-m depth over at least 2 years. Trawling footprint varied markedly among regions: from < 10% of seabed area in Australian and New Zealand waters, the Aleutian Islands, East Bering Sea, South Chile, and Gulf of Alaska to > 50% in some European seas. Overall, 14% of the 7.8 million-km2 study area was trawled, and 86% was not trawled. Trawling activity was aggregated; the most intensively trawled areas accounting for 90% of activity comprised 77% of footprint on average. Regional swept area ratio (SAR; ratio of total swept area trawled annually to total area of region, a metric of trawling intensity) and footprint area were related, providing an approach to estimate regional trawling footprints when highresolution spatial data are unavailable. If SAR was =0.1, as in 8 of 24 regions, therewas > 95% probability that > 90%of seabed was not trawled. If SAR was 7.9, equal to the highest SAR recorded, there was > 95% probability that >70% of seabed was trawled. Footprints were smaller and SAR was =0.25 in regions where fishing rates consistently met international sustainability benchmarks for fish stocks, implying collateral environmental benefits from sustainable fishing. © 2018 National Academy of Sciences. All rights reserved.

© 2018 National Academy of Sciences. All rights reserved. Bottom trawlers land around 19 million tons of fish and invertebrates annually, almost one-quarter of wild marine landings. The extent of bottom trawling footprint (seabed area trawled at least once in a specified region and time period) is often contested but poorly described. We quantify footprints using high-resolution satellite vessel monitoring system (VMS) and logbook data on 24 continental shelves and slopes to 1,000-m depth over at least 2 years. Trawling footprint varied markedly among regions: from < 10% of seabed area in Australian and New Zealand waters, the Aleutian Islands, East Bering Sea, South Chile, and Gulf of Alaska to > 50% in some European seas. Overall, 14% of the 7.8 million-km2 study area was trawled, and 86% was not trawled. Trawling activity was aggregated; the most intensively trawled areas accounting for 90% of activity comprised 77% of footprint on average. Regional swept area ratio (SAR; ratio of total swept area trawled annually to total area of region, a metric of trawling intensity) and footprint area were related, providing an approach to estimate regional trawling footprints when highresolution spatial data are unavailable. If SAR was =0.1, as in 8 of 24 regions, therewas > 95% probability that > 90%of seabed was not trawled. If SAR was 7.9, equal to the highest SAR recorded, there was > 95% probability that >70% of seabed was trawled. Footprints were smaller and SAR was =0.25 in regions where fishing rates consistently met international sustainability benchmarks for fish stocks, implying collateral environmental benefits from sustainable fishing.

This brief highlights the contribution of wild capture fisheries to nutritional security in fish dependent developing countries. It is intended to stimulate debate around two broad themes: (1) when should the focus of fisheries policies be on local food security and human well-being as opposed to revenue generation, and (2) how does the current research agenda, with its emphasis on environmental and economic issues, assist or impair decision making processes.

The spatial distribution of resources and the behavior of a species lead to a spatial pattern of density which has been called the concentration profile of the species. Some species aggregate and may be found almost entirely at high densities, other species space themselves much more uniformly and are usually found at low densities, and some species are found at a very wide range of densities. The interaction between the concentration profile, fishing, and management behavior leads to a number of surprising consequences. Fishermen will naturally tend to fish in the most profitable places, so that the interaction between the concentration profile of the species and the behavior of the fishermen will lead to a complex spatial pattern in abundance, profitability, and catch per unit effort (CPUE). Among the behaviors that emerge from such analysis are (i) overall CPUE will frequently decline more rapidly than abundance, (ii) CPUE will provide almost no information about abundance that can be used for management except on the smallest of spatial scales, and (iii) changes in price or costs of fishing may have significant impacts on the spatial pattern of fishing effort and the associated CPUE. We illustrate these principles in detail with examples from the Tasmanian abalone fishery on a small scale (tens of metres) and a large scale (hundreds of kilometres). Recognition of the concentration profile of the stock suggests that regulatory measures must be carefully tuned to the biology of the species. CPUE will almost certainly be a very poor measure of stock abundance, while fishery-independent surveys will provide the only reliable method of estimating stock status. Complex spatial structure, with differences in growth and mortality will mean that size limits and harvest rates should be finely tuned to the spatial structure of the stock and cannot be set appropriately over large areas. We consider alternative regulatory schemes such as quotas, seasons, size limits, and ter