ALBERT

Description: Large-scale spatial surveys of fish species in relation to habitat have tended to focus on depth, sediment type and temperature as descriptors of fish habitats. At a smaller scale, habitat parameters such as the relief of the sea floor, the presence of structuring fauna and prey availability may have a large influence on fish distribution, but often are not considered. In the present study we used video survey techniques to study habitat components in areas of the English Channel that were known to support consistently high densities of adult plaice. Habitat features were quantified and related to the density of adult plaice caught within the same study areas. To focus the study on habitat components other than sediment type all sites chosen had sandy substrata. The scale and spatial distribution and heterogeneity of physical and biological structures were quantified for each site and correlated to plaice densities. Plaice densities correlated with the abundance of benthic fauna recorded. In particular the emergent tube-dwelling polychaetes Lanice conchilega and Cheatopterus spp., that are a valuable food source for plaice dominated some sites. Abiotic habitat features and habitat heterogeneity showed no clear relationships with respect to plaice densities at the scale of our surveys. This indicated that prey availability might be the driving force for habitat selection of adult plaice within sandy habitats and that other habitat descriptors assume lesser importance at smaller spatial scales.

Description: species, known to occur at other locations within the UK: the crustaceans Caprella mutica and Eriocheirsinensis, ascidians Perophora japonica and Styela clava, the green alga Codium fragile subsp. tomentosoides, and brown algae Sargassum muticum and Undaria pinnatifida. A variety of structures, including pontoon floats, chains and harbour walls were inspected to a depth of 0.5 m for the presence of these non-native species. Seven of the marinas had one or more of the target species. C. mutica wasfound at seven marinas; C. fragile subsp. tomentosoides at two marinas; S. muticum and S. clava were each found at a single marina; E. sinensis, P. japonica and U. pinnatifida were not found. The surveysuggests that recreational boating is an important vector for the dispersal of marine non-native species, and that marinas may act as a refuge for such species. Further and regular port surveys throughout theUK are recommended to provide an effective early warning system for invasive non-native species.

Description: To determine the importance of recreational boating as a vector for distributing marine organisms, including non-native species, the extent of hull fouling species on recreational yachts in Scotland wasassessed. In August 2006, up to 100 yachts in each of the ten largest marinas in Scotland were ranked using a fouling index. 23 yacht owners were asked a questionnaire to determine the importance ofgeneral characteristics of the yacht and its travel history in relation to the level of hull fouling. 59 % of the yachts surveyed were found to have macrofouling attached to their hulls, suggesting that recreationalboating has a high potential for distributing marine species throughout Scotland. Increased age of the antifouling paint, as well as long stationary periods and reduced sailing activity increase the risk ofmacrofouling species attaching to hulls. Recreational boating must be considered as a high risk vector for non-native species in Scotland.

Description: 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.

Description: A habitat specific survey of the epifauna and fish fauna of sandbanks off the Welsh coastline was undertaken in 2001. Of these,three sandbanks were considered to represent extensions of shallow nearshore soft-sediment communities, while a further sixsandbanks were considered to be distinct sandbanks; seabed features clearly defined in comparison with surrounding sediments.Multivariate community analyses revealed that the distinct sandbanks had both fish and epifaunal assemblages that were distinctfrom those sandbanks considered to be extensions of nearshore sediments. The distinct sandbanks were typified by low speciesdiversity and shared indicator species such as the weever fish Echiichthys vipera, the shrimp Philocheras trispinosus and the hermitcrab Pagurus bernhardus. Differences occurred in species composition among the distinct sandbanks, in particular, southernsandbanks were typified by sand sole Solea lascaris and small-eyed ray Raja microocellata. The sandbanks considered as extensionsof nearshore sediments shared many similarities with the Pleuronectes platessaLimanda limanda assemblage, identified by Ellis et al.(Estuar. Coastal Shelf Sci. 51 (2000) 299), which is widespread in the Irish Sea. Sandbanks, as a habitat definition under the EUhabitats directive, are likely to incorporate a number of physically and biologically distinct habitats of which two have beendescribed in the present study.

Description: 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.

Description: Patches of a very dense tube mat biotope were found during fish habitat studies in the eastern English Channel. At three locations in the lows between linear sand banks off the French coast an un-described small Chaetopterus sp. occurred with small Lanice conchilega as an enriched sediment stabilizing biotope. This biotope was distinct though having similarities to other tide swept sub-tidal biotopes dominated by L. conchilega. Using cameras and side-scan sonar it was seen to overlay heterogeneous cobbles and shell hash with intermittent rippled sand veneer. The patchiness of this enriching biogenic feature contributed to the variability in trawl catches of fish.