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Greenstreet, S. P. R., Rogers, S. I., Rice, J. C., Piet, G. J., Guirey, E. J., Fraser, H. M., and Fryer, R. J. 2011. Development of the EcoQO for the North Sea fish community. – ICES Journal of Marine Science, 68: 1–11. Development of the Ecological Quality Objective (EcoQO) for the North Sea demersal fish community is described. Size-based metrics were identified as the most effective indicators of the state of the community, but such metrics are also sensitive to environmental influence. Redefining the large fish indicator (LFI) produced a metric more sensitive to fishing-induced change and therefore more useful to managers. Fish stocks were thought to be exploited at a sustainable rate in the early 1980s, so in a process echoing the precautionary approach to fish stock management, this was considered the reference period for the LFI, suggesting a value of 0.3 as the appropriate EcoQO. The LFI declined from around 0.3 in 1983 to 0.05 in 2001, followed by a recovery to 0.22 in 2008. However, analyses of the longer-term groundfish survey data suggest that, even were fishing pressure to be reduced to early 20th century levels, the LFI would be unlikely to rise much above a value of 0.3. The response of the LFI to variation in fishing pressure suggested a more complex relationship than anticipated, underscoring the need for operational theoretical size-resolved multispecies fish community models to support management towards broader ecosystem objectives.

Fraser, H. M., Greenstreet, S. P. R., and Piet, G. J. 2007. Taking account of catchability in groundfish survey trawls: implications for estimating demersal fish biomass. – ICES Journal of Marine Science, 64. Groundfish surveys are a key component of current scientific data monitoring and data-collection activities undertaken in support of fisheries management. Recent requirements to develop and implement an ecosystem approach to management are placing increasing and varied demands on such datasets. Successfully incorporating ecosystem and environmental objectives within fisheries management will, for example, require greater understanding of foodweb trophodynamics, which in turn requires detailed information on the abundance and distribution of fish predators and prey species on spatial scales hitherto rarely considered. However, no trawl gear catches all the fish in its path, so density estimates provided by such trawl samples do not reflect true densities of fish. Catchability in a trawl gear is affected by many factors and varies both between species and between different sized conspecifics, and therefore has the capacity to confound our understanding of predator–prey interactions and of the relative abundance of different species and size classes of fish at any point in time or space. To overcome such problems, estimates of the catchability of each size class of each species sampled in a given survey are required for trawl sample densities to be raised to the actual densities of fish present at each location sampled. Here, we present a method for estimating catchability coefficients for 1-cm size classes of fish species sampled by the Grande Overture Vertical trawl during the third quarter ICES International Bottom Trawl Survey. The catchability coefficients obtained are applied to survey data collected between 1998 and 2004 to examine annual variation in actual abundance of the demersal fish assemblage in the North Sea.

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

The effect of delayed mating on the reproductive biology of females of the Oriental fruit moth, Grapholita molesta (Busck), was studied in the laboratory. Expected reproduction, defined as t-th day survival rate × percent successful mating × total viable eggs, was reduced by 13, 36, and 74%, respectively, after a 2-, 5-, and 10-d delay in pairing with a male compared with females that were paired with a male on their day of emergence. Female fertility (percentage of females laying fertile eggs), fecundity (total number of eggs laid), egg fertility (percentage of eggs developing to black head stage), and egg hatch (percentage of eggs hatching) were reduced by delays in mating. The pre-oviposition period of females mated within 24 h of emergence was longer than that of females mated 2, 5, or 10 d after emergence. The duration of the oviposition period declined with delays in mating. Female longevity increased with delays in mating and was greatest in virgin females. The number of eggs laid per day was similar in females paired with a male 2, 5, and 10 d after their emergence. Commencing 2 d after pairing, females paired on their day of emergence exhibited a daily oviposition rate similar to that of females paired 2–10 d after emergence. These observations suggest that the successful control of the Oriental fruit moth using sex-pheromone-mediated orientation disruption (mating disruption) is more likely accomplished by preventing mating than by delaying mating.