Sandeel abundance and sediment particle size data from 2886 grab samples collected during 14 surveys undertaken in the Wee Bankie/Marr Bank region of the north-western North Sea between 1998 and 2003 are analysed. Odds Ratio, an analysis that compares the proportion of all samples assigned to a particular sediment category, with the proportion of samples containing sandeels assigned to the same category, reveals clear patterns of either selection for, or avoidance of, seabed habitats containing varying proportions of 8 sediment particle size categories. As the proportion of Coarse Gravel, Fine Gravel, Fine Sand, Coarse Silt, Medium Silt and Fine Silt in the seabed habitat increases, sandeels show reduced selection for and increased avoidance of the habitat. Conversely, as the proportion of Coarse Sand and Medium Sand in the sediment increases, sandeels show reduced avoidance of and increased selection for the habitat. Classification Tree and Principal Components Analysis define 8 types of seabed habitat on the basis of their sediment particle size composition that vary in sandeel occupancy rate, sandeel density and the size of sandeels that occupy the habitat. Variation in sandeel density across these 8 habitat types is primarily influenced by the silt content in the sediment. Variation in the size of sandeels occupying each habitat type is mainly dictated by the coarseness of the sediment. The value of such results for the design of grab surveys intended to monitor variation in local sandeel abundance is discussed.KEY WORDS: Ammodytes marinus · Sandeel · Habitat preference · Sediment particle size Resale or republication not permitted without written consent of the publisher

J. 2006. Variation in the abundance of sandeels Ammodytes marinus off southeast Scotland: an evaluation of area-closure fisheries management and stock abundance assessment methods. e ICES Journal of Marine Science, 63: 1530e1550.In 2000, a sandeel fishery off SE Scotland, which commenced in the early 1990s, was closed in response to concerns that the fishery was having a deleterious effect on seabird breeding performance at colonies in the vicinity of the fishing grounds. Fishery-derived catch per unit effort (cpue) data are used together with three different fishery-independent survey techniques (acoustic, demersal trawl, and nocturnal grab survey) to assess variation in sandeel Ammodytes marinus population biomass in the area over the period 1997e2003, a period that included the last three years that the fishery was operating and the first four years of the sandeel fishing moratorium. Temporal trends in estimates of sandeel biomass derived from these different assessment methods were inconsistent and, on the basis of these alone, it was not possible to determine whether sandeel population biomass in the area had increased following the closure of the fishery. The different survey methods assess different components of the sandeel population; acoustic survey and fishery cpue quantified sandeels active in the water column, whilst demersal trawl survey quantified sandeels buried in the sediments. These data were collected at a time of year when sandeels were moving between the seabed sediments and the overlying water column. A grab survey also quantified sandeels buried in the sediment, but these data were collected at a time of year when the entire population should have been buried in the sediment. Differences between the different timeseries were reconciled by taking account of the cumulative total primary production in each year prior to the surveys. On the basis of this, a model was developed that utilized acoustic and demersal trawl survey data to estimate the total sandeel population biomass. This model was validated using the nocturnal grab-survey data. The modelled data indicated that the biomass of sandeels 1þ years old increased sharply in the first year of the closure and remained higher in all four of the closure years than in any of the preceding three years, when the fishery was operating. The biomass of 0-group sandeels in three of the four closure years exceeded the biomass present in the three years of commercial fishing. Whereas the response of 1þ sandeels may have been a direct consequence of the closure, this is not likely to have been the case in respect of 0-group sandeels. The closure appears to have coincided with a period of enhanced recruit production.

Greenstreet, S. P. R., Holland, G. J., Guirey, E. J., Armstrong, E., Fraser, H. M., and Gibb, I. M. 2010. Combining hydroacoustic seabed survey and grab sampling techniques to assess “local” sandeel population abundance. – ICES Journal of Marine Science, 67: 971–984. Sandeels (Ammodytes marinus) are a critical prey of many top predators in the North Sea, and have also been the target of a major industrial fishery. To quantify resource allocation between competing predators, and between natural predators and fishers, and to assess the impact of each source of mortality on sandeel population dynamics, estimates of the absolute abundance of sandeels at the spatial scale at which these interactions take place are required. In this study, hydroacoustic seabed survey and nocturnal grab surveys are combined to examine variation in the abundance of sandeels at a sandbank complex off southeast Scotland. Grab surveys provide point estimates of sandeel density and sediment composition data, which are used to define sandeel sediment preference categories. The total area of each sandeel sediment preference category is determined by hydroacoustic seabed survey. Sandeel population abundance recovered immediately following the closure of the sandeel fishery. However, simply closing the fishery was not sufficient to maintain the size of the local sandeel stock; the population is also highly dependent on good recruitment. We demonstrate how this combination of techniques might be used to examine variation in overwintering mortality rates in sandeels.

Greenstreet, S. P. R., Holland, G. J., Fraser, T. W. K., and Allen, V. J. 2009. Modelling demersal fishing effort based on landings and days absence from port, to generate indicators of “activity”. – ICES Journal of Marine Science, 66: 886–901. For many components of marine ecosystems, the derivation of biologically significant, operational “pressure” indicators will rely on modelling fishing mortality from indicators of anthropogenic “activity”. This essentially expands the well established Pressure–State–Response framework to one of Activity–Pressure–State–Response. Within the Common Fisheries Policy, the reporting of fishing effort data, the basic indicator of activity, is not mandatory. A modelling approach is therefore developed that utilizes the data that fishers are obliged to report (days absence from port, landings from each rectangle fished, and the gear used) to provide modelled estimates of fishing effort. The model is parameterized for the Scottish demersal fishing fleet using data collected through the Scottish discards observer scheme, and fishing effort over the period 1997–2004 is modelled. Reported effort data for the period 1960–1998 allowed validation of the model through direct comparison of modelled with reported data in 1997 and 1998. Combining the modelled and reported datasets revealed that Scottish fishing activity levels, remarkably constant over four decades, had declined markedly since 2000. Temporal trends in UK quotas for the main targeted demersal species are considered to assess the effectiveness of catch limitation management as a means of regulating fishing activity. Spatial patterns in effort by the four main gear types used by the Scottish demersal fleet are described, and in general terms, these have changed little over the period 1960–2004. However, distinct spatial patterns emerged in the temporal trends in each ICES rectangle, associated with the recent overall decline in Scottish demersal fishing activity. These patterns were not intuitive, and the implications of this for an ecosystem approach to management are discussed.