Bottom trawl fishing footprints on the world’s continental shelves

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 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

Distribution and abundance patterns of two parapagurid hermit crabs (Crustacea: Decapoda: Anomura) along the west and south coasts of South Africa

series of over 6 000 research-trawl samples collected along the west and south coasts of South Africa between 1987 and 2014 were analysed for the presence and biomass of two parapagurid hermit crabs, Sympagurus dimorphus and Parapagurus bouvieri. The percentage of trawls that landed S. dimorphus and P. bouvieri and the mean caught biomass were higher on the west than on the south coast for both the more-abundant S. dimorphus (30.59 vs 5.81% success and 287.88 vs 31.37 kg km–2, respectively) and for the less-abundant P. bouvieri (13.76 vs 3.58% success and 38.56 vs 16.32 kg km–2, respectively). Very few parapagurids were caught shallower than 150 m; thereafter, the proportion of trawls containing hermit crabs increased, peaking over the depth range 201–250 m for S. dimorphus (54%) and 401–450 m for P. bouvieri (51%), and declining steadily thereafter. On the west coast, the relative caught biomass of S. dimorphus increased significantly from north to south, but there was no apparent latitudinal trend in relative biomass for P. bouvieri. Similarly, there was a significant decline in caught biomass of S. dimorphus with increasing longitude along the south coast, but no apparent trend for P. bouvieri. Although this represents by far the most comprehensive global analyses of distribution and abundance patterns for parapagurids to date, extremely little remains known about the biology and ecological relationships of these species, or indeed of other members of the group. Keywords: benthic invertebrates, biogeography, biomass, depth distribution, latitudinal trend, Parapagurus bouvieri, research trawls,Sympagurus dimorphu

A knowledge base for management of the capital-intensive fishery for small pelagic fish off South Africa

As a contribution to South Africa's move towards an ecosystem approach to fisheries management, this study explores the existence of common perceptions about South Africa's pelagic fishery between resource users and scientists. It represents a collaborative research effort of social and natural scientists. A brief overview is given of the southern Benguela upwelling ecosystem and small pelagic fish resources, the fishery, and management of the fishery. Stakeholder knowledge and views were determined by conducting open-ended qualitative local knowledge interviews. Candidate indicators to address five major issues raised in the interviews were selected: length-at-50% maturity, total mortality, exploitation rate, proportion of bycatch, mean length of catch, and centre of gravity of catches. The indicator approach is shown to be a useful tool to manage the South African small pelagic fishery, and can be made compatible with existing management approaches. The foundation of a good adaptive fisheries management system is a data collection system that enables multi-disciplinary analysis and provides a basis on which decisions can be made. Keywords: anchovy, ecosystem approach, formal knowledge, industrial fishery, informal knowledge, management, pelagic, sardine, South AfricaAfrican Journal of Marine Science 2006, 28(3&4): 645–66