ALBERT

Beschreibung: Flatfishes have been the subject of scientific research since the beginning of the 19th century but information on the specific habitat requirement of the adult life stages is largely anecdotal. Detailed knowledge of flatfish habitats however is a precondition for a more ecosystem orientated approach to fisheries management. Here the association between benthic habitat and the adult life stage of three flatfish species plaice (Pleuronectes platessa), sole (Solea solea) and lemon sole (Microstomus kitt) was investigated in the English Channel. Data from groundfish surveys spanning a period of 9 years was used to identify three distinct site groups: sites where a species occurred in consistently high abundances, sites of variable or low abundance and sites at which none were caught. Following the supposition of habitat selection theories such as the ideal free distribution theory these three sites groups should represent a gradient in habitat suitability from highly suitable to less suitable and unsuitable respectively. Habitat parameters and features for the three site groups and species were described and analysed. In particular sediment type and the importance of structuring epifauna for adult flatfish was investigated. Overall plaice and sole showed very similar trends for abiotic environmental parameters such as depth, temperature, salinity and tidal currents. Lemon sole was found over distinctly different habitats which may indicate a stronger niche partitioning of this species. Sediment associations differed between the three species with plaice predominantly occurring over sandy substrates with little mud and gravel content, while sole was found over a wider range of muddy to sandy substrates. Lemon sole was predominantly found over sand however containing a higher percentage of gravel than plaice. Structuring emergent epifauna was related positively to plaice and lemon sole abundances. These structures might be important as they tend to harbour larger numbers of epibenthic species upon which adult plaice and lemon sole prey. No such trend was found for the tactile feeding sole which mainly forages on infaunal polychaetes and molluscs.

Beschreibung: Demersal fish assemblages are intimately associated with benthic habitats where they spend a large part of their time feeding and avoiding predators. Bottom fishing activities can degrade seabed habitats and change benthic communities by reducing their complexity. Thereby they can also degrade essential fish habitats such that they can no longer sustain the fish species associated with them. Having established a relationship between cod (Gadus morhua) and whiting (Merlangius merlangus) and specific Irish Sea habitats from consultation with fishers and ground fish surveys we wanted to learn what functional role these habitats play, i.e. as sources of prey and shelter from predators. Habitats complexity of stations with high and medium fish densities was assessed using side scan sonar, QTC ViewTM and underwater photography. Young cod were particularly abundant in a habitat with mixed sediments (low grain size sediments between stones and shells) and emergent epifauna off Belfast Lough (Northern Ireland). Dietary specialism indicates a close association with a particular habitat, while broader diets within and between different areas indicate a weaker association of a fish species with a particular habitat. The availability of prey organisms was assessed by sampling epifaunal and infaunal organisms with a 2-m beam trawl and a Day grab. Demersal fish for condition and stomach contents analysis were collected by otter and beam-trawling. The results from stomach content analysis of cod and whiting are discussed in relation to the prey availability found in the study areas and food niche breadth.

Beschreibung: Fishers have often complained that standard United Kingdom groundfish survey data do notadequately reflect the grounds targeted by commercial fishers, and hence, scientists tend to make overcautiousestimates of fish abundance. Such criticisms are of particular importance if we are to make acreditable attempt to classify potential essential fish habitat (EFH) using existing data from groundfishsurveys. Nevertheless, these data sets provide a powerful tool to examine temporal abundance of fishon a large spatial scale. Here, we report a questionnaire-type survey of fishers (20012002) that invitedthem to plot the location of grounds of key importance in the Irish Sea and to comment on key habitatfeatures that might constitute EFH for Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus,and European whiting Merlangius merlangus. Plotted grounds were cross-checked using records ofvessel sightings by fishery protection aircraft (19851999). A comparison of the areas of seabedhighlighted by fishers and the observations made on groundfish surveys were broadly compatible forall three species of gadoids examined. Both methods indicated important grounds for cod and Europeanwhiting off northern Wales, the Ribble estuary, Solway Firth, north of Dublin, and Belfast Lough. Themajority of vessel sightings by aircraft did not match the areas plotted by fishers. However, fishingrestrictions, adverse weather conditions, and seasonal variation of fish stocks may have forced fishersto operate outside their favored areas on the (few) occasions that they had been recorded by aircraft.Fishers provided biological observations that were consistent among several independent sources (e.g.,the occurrence of haddock over brittle star [ophiuroid] beds). We conclude that fishers knowledge isa useful supplement to existing data sets that can better focus more detailed EFH studies.

Beschreibung: Fishers have often complained that standard fisheries survey data do not adequately reflect the grounds targeted by commercial fishers and hence scientists tend to make over-cautious estimates of fish abundance. Such criticisms are of particular importance if we are to make a creditable attempt to classify 'Essential Fish Habitat' using existing large-scale standard trawl surveys. Nevertheless, these datasets provide a powerful tool to examine consistent patterns in the temporal abundance of fish on a spatial scale. Here, we report a questionnaire survey of fishers that invited them to indicate the location of grounds of key importance for gadoid fishes. In addition, fishers were asked to indicate whether they had noticed key habitat features that might indicate the characteristics of EFH. A comparison of such areas as highlighted by fishers with data from standard groundfish surveys were broadly compatible for all three species of gadoids examined. Many sampling stations of these surveys fell outside areas highlighted by fishers as key fishing grounds/habitats. Fishers were able to provide usable biological observations that were consistently cross-referenced by several independent sources, for example the occurrence of haddock over brittlestar beds. We conclude that fishers' knowledge is an invaluable supplement to existing datasets that can help to better focus more detailed studies of EFH.

Beschreibung: In recent years, there has been an increasing interest in the protection of sea bed habitats that are important for commercially exploited fish species ('Essential Fish Habitats', EFH) and may be vulnerable to anthropogenic activities such as bottom fishing or aggregate extraction. Locating such habitats in the vast space of the sea, however, is difficult. The concept of habitat selection based on 'Ideal free distribution' theory suggests that areas of high suitability may attract larger quantities of fish than less suitable or unsuitable areas. Here, we used catch data from groundfish surveys to identify areas of consistently high densities of whiting (Merlangius merlangus), cod (Gadus morhua), haddock (Melanogrammus aeglefinus), in the Irish Sea and plaice (Pleuronectes platessa), sole (Solea solea), lemon sole (Microstomus kitt) in the English Channel over a period of 9 and 10 years respectively.A method was developed to identify areas of the seabed that may constitute EFHs and may therefore merit further investigations. In addition, the number of potential EFHs identified and the number of stations where no fish were caught gave an indication of the site specificity of the fish species analysed. For the gadoids, whiting was found to be less site specific than cod and haddock, while for the flatfish plaice and sole were less site specific then lemon sole. Our findings are discussed in the context of previously published studies on dietary specialism. The site specificity of demersal fish has implications for the siting process for marine protected areas as fish species with a strong habitat affinity can be expected to benefit more from such management schemes.

Beschreibung: There is increasing interest in the use of marine protected areas (MPAs) as tools to achieve the goal of ecosystem management. MPAs could counteract these effects by limiting the impact on areas important for feeding, shelter, spawning and migration. Thus MPAs should include features that enable fish to reach maturity and thus contribute to the spawning stock. But how do we find the most suitable habitats for fish species in large marine areas? Ecological theory (ideal free distribution) suggests that fish will be most abundant in areas that have the most favourable habitat characteristics for that species. Fish stock assessment data could be used to assess where fish species consistently tend to aggregate. In this study we examined stock assessment data collected for three flatfish species (plaice, sole and lemon sole) from 134 stations in the English Channel over nine years. Juvenile fish were excluded from the analysis. The fish abundance data for each year was ranked and the mean rank calculated. The coefficient of variation of the mean rank score had the least variability at stations with the highest mean rank scores and also at those with the lowest rank scores. Stations that had a mid-range mean rank had the greatest inter-annual variation. It would appear that stations with the highest mean rank abundance consistently attract fish. Such areas may be the prime focus for potential MPAs