The Woods Hole bottom-trawl resource survey: development of fisheries-independent multispecies monitoring

Multispecies bottom-trawl resource surveys have been conducted since at least 1885, with substantial development since 1948. The post-World War II development of this survey methodology was similar to the original development, with a focus on the effects of fishing and the nature of ecological interactions. Surveys were initially conducted by individual fisheries laboratories following systematic survey designs, each employing a single vessel and a standard trawl configuration. The data were shown to be useful in monitoring the status of stocks and in simultaneously providing information for addressing technical and ecological interactions. Attempts to design multinational trawl surveys proved difficult, primarily on the point of standardization. This is in marked contrast to other fishery-independent methods of measuring abundance, such as hydroacoustic surveys for pelagic fishes and sighting surveys for cetaceans. Although various attempts have been made at standardization of trawl surveys, the results in the end depend on not only the net, but also the vessel and its configuration. Although the lack of development of a standardized methodology has limited the generality of this approach, long-term single-nation and international multispecies trawl surveys have been used to monitor changes in fish abundance and size and species composition in many areas since at least 1963.