Mike Armstrong, co-chair of the Benchmark Workshop for Sea Bass (WKBASS)
'ICES provides advice each year on the state of fish stocks in European waters, as well as options for future fishing opportunities in line with the principles of sustainable fishing. Where does ICES obtain the evidence to support its advice? Fish, invertebrates and their predators are largely out of sight below the water surface and it is clearly impossible to count and measure all the individuals in the population. We must sample the population to find evidence for changes that are taking place. The main sources of data are from the fisheries themselves and from sampling programmes independent of the fisheries.
Fishery-dependent data include mandatory data on catches and fishing activities supplied by fishing skippers, as well as representative sampling of fishing trips to estimate discarded and recreational catches not reported through logbooks. In some fisheries, the trends in quantities caught per unit of fishing effort (e.g. per day) can provide evidence on trends in stock abundance. Sampling on shore and at sea provides information on the size and (where possible) age of individuals in the catches. These data can be used to estimate the annual fishing mortality rate, an indicator of the proportion of the stock removed by fishing during the year which can be compared with values considered sustainable.
Fishery-independent data are collected, for example, from research vessels using trawls, acoustic systems, underwater cameras and planktonic egg samplers to collect data on abundance and composition at stations or transects positioned randomly or systematically across the geographic range of the stock. Many such surveys also provide other data on the ecosystem. Fishery-independent data can be used on their own to provide advice on stock trends, but ICES often includes them with fishery-dependent data in assessments to provide the most accurate estimates of stock trends, stock status and future fishing opportunities.'