Domingo Lloris

Deep-sea fish assemblages in the Catalan Sea (western Mediterranean) below a depth of 1000 m

Abstract The analysis of 48 bottom trawl collections from the Catalan Sea below a depth of 1000 m has allowed the identification of two distinct demersal fish assemblages, occurring on the middle and lower slope. The Middle Slope Assemblage (MSA) and Lower Slope Assemblage (LSA), restricted to the middle (1000–1425 m) and lower (1425–2250 m) slope, respectively, each consist of two groups with distinct structures. While one group is relatively homogeneous, the other can be considered as comprising a faunal transition. Each assemblage is dominated by species possessing very different characteristics. The preponderance of middle and large size fish with high energy requirements in the MSA is replaced, in the LSA, by smaller and more passive species with lower energy requirements. These differences are reflected in a series of ecological parameters such as abundance, biomass, mean fish weight, species richness and mean species richness. A pronounced decrease in the value of these parameters is generally seen with increasing depth, reflecting the increasingly oligotrophic conditions. Furthermore, the highly stable environmental conditions of the western Mediterranean (where water temperature and salinity rarely change below a depth of 150 m), suggest that the observed zonations may be determined by biological factors. It is possible to relate the observed faunistic changes with the vertical distribution of mesopelagic organisms. These organisms play a fundamental role in the feeding ecology of demersal fish species of the slope, either directly as prey or indirectly by enriching the sediments, and thus determining the distribution of sedimentivorous invertebrate species.

Deep-living demersal fishes in the Catalan Sea (western Mediterranean) below a depth of 1000 m

An extensive survey of the deep-living fishes of the Catalan Sea (western Mediterranean) recorded 31 species in 19 families and 29 genera from 100 samples at depths between 960 and 2251 m. Chlorophthalmidae, Moridae and Macrouridae accounted for nearly 85% of all specimens taken. In biomass terms, Hexanchidae, Moridae, Alepocephalidae and Chlorophthalmidae were the most important families. A quantitative model of the bathymetric distribution of the species is presented. The ‘centre of gravity’ of species’ distribution and the habitat width, a measure of the distribution heterogeneity, are also given. Out of the 31 demersal species caught, the distributions of only 13 are centered below 1000 m. The Mediterranean deep-sea ichthyofauna is very impoverished in comparison with the adjacent Atlantic Basin fauna.

Jelly-falls historic and recent observations: a review to drive future research directions

The biological pump describes the transport of particulate matter from the sea surface to the ocean’s interior including the seabed. The contribution by gelatinous zooplankton bodies as particulate organic matter (POM) vectors (“jelly-falls”) has been neglected owing to technical and spatiotemporal sampling limitations. Here, we assess the existing evidence on jelly-falls from early ocean observations to present times. The seasonality of jelly-falls indicates that they mostly occur after periods of strong upwelling and/or spring blooms in temperate/subpolar zones and during late spring/early summer. A conceptual model helps to define a jelly-fall based on empirical and field observations of biogeochemical and ecological processes. We then compile and discuss existing strategic and observational oceanographic techniques that could be implemented to further jelly-falls research. Seabed video- and photography-based studies deliver the best results, and the correct use of fishing techniques, such as trawling, could provide comprehensive regional datasets. We conclude by considering the possibility of increased gelatinous biomasses in the future ocean induced by upper ocean processes favouring their populations, thus increasing jelly-POM downward transport. We suggest that this could provide a “natural compensation” for predicted losses in pelagic POM with respect to fuelling benthic ecosystems.

Sinking jelly-carbon unveils potential environmental variability along a continental margin.

Particulate matter export fuels benthic ecosystems in continental margins and the deep sea, removing carbon from the upper ocean. Gelatinous zooplankton biomass provides a fast carbon vector that has been poorly studied. Observational data of a large-scale benthic trawling survey from 1994 to 2005 provided a unique opportunity to quantify jelly-carbon along an entire continental margin in the Mediterranean Sea and to assess potential links with biological and physical variables. Biomass depositions were sampled in shelves, slopes and canyons with peaks above 1000 carcasses per trawl, translating to standing stock values between 0.3 and 1.4 mg C m2 after trawling and integrating between 30,000 and 175,000 m2 of seabed. The benthopelagic jelly-carbon spatial distribution from the shelf to the canyons may be explained by atmospheric forcing related with NAO events and dense shelf water cascading, which are both known from the open Mediterranean. Over the decadal scale, we show that the jelly-carbon depositions temporal variability paralleled hydroclimate modifications, and that the enhanced jelly-carbon deposits are connected to a temperature-driven system where chlorophyll plays a minor role. Our results highlight the importance of gelatinous groups as indicators of large-scale ecosystem change, where jelly-carbon depositions play an important role in carbon and energy transport to benthic systems.

Description of Merluccius tasmanicus sp. nov. and redescription of Merluccius australis (Pisces: Merlucciidae)

A new hake species, Merluccius tasmanicus sp. nov., is described from New Zealand waters and another species, Merluccius australis is redescribed. Merluccius tasmanicus sp. nov. differs from all other congeneric species in the following combination of characters: upper profile of the head slowly concave; lateral line slowly concave in the caudal region; body depth 4.9-5.9 times in standard length (SL); orbital diameter 6.1-7.1 times in head length, 2.1-2.2 times in snout length and 1.6-1.9 times in interorbital width; second dorsal fin rays, 42-43; anal fin rays, 42-44; lateral line scales ∼164. Merluccius australis is redescribed to clarify the identity of this species. Merluccius australis differs from all other congeneric species in the following combination of characters: upper profile of the head straight; lateral line straight in the caudal region; body depth 6.6-7.1 times in SL; orbital diameter 4.5-5.4 times in head length, 1.2-1.7 times in snout length and 1.0-1.3 times in interorbital width; second dorsal fin rays, 40-43; anal fin rays, 40-43; lateral line scales, more than 155. Merluccius tasmanicus sp. nov. is found in New Zealand and Patagonian waters and occasionally in Japanese waters; Merluccius australis is reported in both New Zealand and Patagonian waters.

First record of Solea (Microchirus) boscanion (Osteichthyes: Soleidae) in the Mediterranean Sea, with data on other sympatric soleid species

The capture of ¢ve specimens of Solea (Microchirus) boscanion (Osteichthyes: Soleidae), a species previously unrecorded in the Mediterranean, is reported from the Iberian coast (western Mediterranean). The main morphometric and meristic measurements of this species with data of the other sympatric, and morphologically very similar, soleids Microchirus variegatus and Buglossidium luteum are also given.The record is discussed in relation to climate change and competition between species.

Distribution pattern of Galeus atlanticus in the Alborán Sea (south western Mediterranean) and some sexual character comparison with Galeus melastomus

Abstract Galeus atlanticus is a small-sized deepwater catshark living on the slope bottom of the Alborán Sea. Given its external similarities with Galeus melastomus, both species are often confused, which makes G. atlanticus a very poorly understood species both in terms of catches and biological aspects. For this study, a total of 741 G. atlanticus specimens, caught during scientific surveys from 1997 to 2003, were analysed. The distributional patterns were described and the reproductive status estimated. Galeus atlanticus occurred throughout the Alborán Sea, between the Strait of Gibraltar and Cape Gata, including the slope of the Island of Alborán. Its bathymetric range extended from 330 to 790 m and no size–depth trends have been observed. Mature specimens, both males and females, were caught in all seasons of the year. Size at first maturity was significantly different between sexes, with estimates of 32.9 cm for males and 36.9 cm for females. The differential growth of some secondary sexual characteristics, such as clasper length in males and oviducal gland diameter in females, were compared with those of G. melastomus.

Spatial distribution of ichthyofauna in the northern Alboran Sea (western Mediterranean)

This study describes the four main demersal fish assemblages identified along the continental shelf and slope (30–800 m depth) of the northern Alboran Sea (western Mediterranean), based on the analysis of the MEDITS (International bottom trawl survey in the Mediterranean) 12-year data series. We collected 186 fish species belonging to three classes, 24 orders and 69 families. Taxonomically, the order Perciformes was the most diverse, represented by 18 families and 58 species. Each assemblage had particular characteristics of abundance, biomass, mean fish weight and species richness. The geographical differences associated with the distribution of some species occurred within shelf assemblages. The middle slope was characterised by the highest similarity between samples, probably due to its lower environmental variability compared to that of the other assemblages.

A new species of Nansenia (N. problematica) (Salmoniformes: Bathylagidae) from the Southeast Atlantic

We are grateful to the following curators for the loan of specimens used in this study: C. W. Myers and R. G. Zweifel (American Museum of Natural History AMNH), R. F. Inger (Field Museum of Natural History CNHM), J. W. Wright (Natural History Museum of Los Angeles County (LACM), P. Alberch (Museum of Comparative Zoology MCZ), D. F. Hoffmeister (University of Illinois Museum of Natural History UIMNH), W. R. Heyer (United States National Museum USNM) andJ. A. Campbell (Collection of Vertebrates, University of Texas at Arlington UTA). S. D. Busack, H. W. Greene, D. B. Wake and M. H. Wake critically read the manuscript. G. M. Christman prepared Figs. 2 and 3. Field work was supported by grants from the Department of Zoology and the Museum of Vertebrate Zoology, University of California, Berkeley, to the junior author. Thejunior author also wishes to thank Gerhard Roth for his help and fine companionship in Mexico. Research was supported in part by NSF Grant DEB 80-05905 to M. H. Wake. acional, 2,600-2,700 m (MVZ 109492-93, 8981); 4.3 km Ejct. Mex. Hwy. 105 and old y. to Tianguistengo, 1,950 m (3 uncatagued MVZ specimens); 3.2 km by rd NW Agua lanca, 2,150 m (2 uncatalogued MVZ speciLITERATURE CITED