This study assesses the seabed pressure of towed fishing gears and models the physical impact (area and depth of seabed penetration) from trip-based information of vessel size, gear type, and catch. Traditionally fishing pressures are calculated top-down by making use of large-scale statistics such as logbook data. Here, we take a different approach starting from the gear itself (design and dimensions) to estimate the physical interactions with the seabed at the level of the individual fishing operation. We defined 14 distinct towed gear groups in European waters (eight otter trawl groups, three beam trawl groups, two demersal seine groups, and one dredge group), for which we established gear “footprints”. The footprint of a gear is defined as the relative contribution from individual larger gear components, such as trawl doors, sweeps, and groundgear, to the total area and severity of the gear's impact. An industry-based survey covering 13 countries provided the basis for estimating the relative impact-area contributions from individual gear components, whereas sediment penetration was estimated based on a literature review. For each gear group, a vessel size–gear size relationship was estimated to enable the prediction of gear footprint area and sediment penetration from vessel size. Application of these relationships with average vessel sizes and towing speeds provided hourly swept-area estimates by métier. Scottish seining has the largest overall gear footprint of ∼1.6 km 2 h −1 of which 0.08 km 2 has an impact at the subsurface level (sediment penetration ≥ 2 cm). Beam trawling for flatfish ranks low when comparing overall footprint size/hour but ranks substantially higher when comparing only impact at the subsurface level (0.19 km 2 h −1 ). These results have substantial implications for the definition, estimation, and monitoring of fishing pressure indicators, which are discussed in the context of an ecosystem approach to fisheries management.

Abstract.A phylogenetic approach to the origin and maintenance of species diversity ideally requires the sampling of all species within a clade, confirmation that they are evolutionarily distinct entities, and knowledge of their geographical distributions. In the marine tropics such studies have mostly been of fish and reef-associated organisms, usually with high dispersal. In contrast, snails of the genus Echinolittorina (Littorinidae) are restricted to rocky shores, have a four-week pelagic development (and recorded dispersal up to 1400 km), and show different evolutionary patterns. We present a complete molecular phylogeny of Echinolittorina, derived from Bayesian analysis of sequences from nuclear 28S rRNA and mitochondrial 12S rRNA and COI genes (nodal support indicated by posterior probabilities, maximum likelihood, and neighbor-joining bootstrap). This consists of 59 evolutionarily significant units (ESUs), including all 50 known taxonomic species. The 26 ESUs found in the Indo-West Pacific region form a single clade, whereas the eastern Pacific and Atlantic species are basal. The earliest fossil occurred in the Tethys during the middle Eocene and we suggest that the Indo-West Pacific clade has been isolated since closure of the Tethyan seaway in the early Miocene. The geographical distributions of all species (based on more than 3700 locality records) appear to be circumscribed by barriers of low temperature, unsuitable sedimentary habitat, stretches of open water exceeding about 1400 km, and differences in oceanographic conditions on the continuum between oceanic and continental. The geographical ranges of sister species show little or no overlap, indicating that the speciation mode is predominantly allopatric. Furthermore, range expansion following speciation appears to have been limited, because a high degree of allopatry is maintained through three to five branching points of the phylogeny. This may be explained by infrequent long-distance colonization, habitat specialization on the oceanic/continental gradient, and perhaps by interspecific competition. In the eastern Pacific plus Atlantic we identify five cases of divergence on either side of the Isthmus of Panama, but our estimates of their ages pre-date the emergence of the Isthmus. There are three examples of sister relationships between species in the western Atlantic and eastern Atlantic, all resulting from dispersal to the east. Within the Indo-West Pacific, we find no geographical pattern of speciation events; narrowly endemic species of recent origin are present in both peripheral and central parts of the region. Evidence from estimated divergence times of sister species, and from a plot of the number of lineages over time, suggest that there has been no acceleration of diversification during the glacio-eustatic cycles of the Plio-Pleistocene. In comparison with reefal organisms, species of Echinolittorina on rocky shores may be less susceptible to extinction or isolation during sea-level fluctuations. The species richness of Echinolittorina...

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Observations made in the scientific and popular literature suggest that the characteristics of both marine and terrestrial ecosystems are changing rapidly due to increasing global air and sea temperatures. Here, we examine the hypothesis that fish species with more 'southern' distributions are increasing in the northern North Sea over time. In order to do this, 2 important databases on fish abundance collected by trawl on research cruises are interrogated. When combined, the databases cover both the entire North Sea and the Scottish west coast and span a period of 80 yr (1925 to 2004). The data take the form of length-frequencies for all species caught (> 300 different species), while additional information (e.g. age, sex, weight and stage of sexual maturity) is available for the commercially important component (e.g. cod). The trawl data suggest that the North Sea is experiencing waves of immigration by exotic, southern species (e.g. red mullet, anchovy and pilchard). The purpose of this paper is to describe and document these changes.KEY WORDS: Anchovy · Sardine · Horse mackerel · Mackerel · Long-term · North Sea · Climate Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 284: [269][270][271][272][273][274][275][276][277][278] 2004 doliolids are connected to unusual incursions of oceanic water caused by changes in the North Atlantic Oscillation (Edwards et al. 1999).Higher than average sea temperatures are correlated with low recruitment of cod at the latitudinal limits of its range (Planque & Frédou 1999, O'Brien et al. 2000. Reid et al. (2001) related abrupt changes in the abundance and composition of the plankton and fish community ca. 1988 to recent increases in the North Sea horse mackerel fishery. Pronounced increases in tropical fish in the Bay of Biscay area have been noted (Quero et al. 1998) by scientists in France, while Swaby & Potts (1999) made the first British record of the sailfin dory Zenopsis conchifer, noting that the species is advancing northwards along the continental shelf west of the British Isles at a rate of 60 km per decade. Other studies show similar patterns. Information on first records of southerly fish species caught in Cornish waters has been collated and published (Stebbing et al. 2002), and nearly 20 completely new species have been recorded (by 2001). The fish species noted include bigeyed tunny Thunnus obesus, sailfin dory Zenopsis conchifer, short-nosed seahorse Hippocampus hippocampus and barracuda Sphyraena sphyraena. In the Irish Sea, the occurrence of the warm-water species, anchovy Engraulis encrasicolus, has increased between 1990 and 1998 according to trawl data from research surveys (Armstrong et al. 1999). British commercial fishermen have also noted change. The spider-crab Maia squinado fishery, for example, is advancing steadily further northwards (Anonymous 2003).In 1996, a paper was published describing the longterm variation in the abundance of southern species in the southern North Sea (Corten & van...

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An account is given of the comparative morphology of the family Littorinidae, based on examination of 122 species, grouped into 32 subgenera. The shell, operculum and principal organ systems are described, and their phylogenetic significance assessed. A total of 53 characters, coded as 131 character states, were chosen for inclusion in a cladistic analysis of the phylogenetic relationships of the subgenera. This was performed by the program paup, using the principle of maximum parsimony. The outgroup for the analysis comprised representatives of the Pomatiasidae and Skeneopsidae. A consensus tree was obtained from cladograms with consistency indices of 0.408 (autapomorphies excluded).