Body fish size tendencies within and among species in the deep-sea of the western Mediterranean

Abstract

SUMMARY: Data collected south-west of the Balearic Islands (Western Mediterranean) on two cruises, Quimera-I (October, 1996) and Quimera-II (May, 1998), were used to establish general ecological patterns in deep-sea fish assemblages. A total of 39 trawls were taken at depths between 400 and 1714 m. Fish assemblages were analysed in terms of species composition, ecological parameters and biomass spectra. Differences in species composition between cruises and depth (Upper slope: 400-800 m, Middle slope: 801-1400 m and Lower slope: 1401-1714 m depth) were evaluated using multivariariate analysis. The most important feature was the existence of a biomass peak at intermediate depths. Moreover, the analysis of the biomass spectra indicated the absence of large individuals at the shallower depth interval considered. To determine the causes of the biomass peak on the middle slope four hypothesis were explored: (1) species richness is higher on the middle slope; (2) the fish assemblage from the middle slope can be characterised by the highest abundance (number of fish/area); (3) species found on the middle slope are larger (the species assemblage is built up by larger species); and (4) there is a trend for the specimens of several species to be larger at the middle slope. The data gathered support that the biomass peak is better explained by the existence of abundance peaks of medium and large-sized species, and by the presence of some of the largest individuals of other large-sized species, in both cases related to specific depth size trends which do not always follow a bigger-deeper trend.

Distribution and biology of the Blackmouth catshark Galeus melastomus in the Strait of Sicily (Central Mediterranean Sea)

“…the large specimens detected below 600 m in the NW-Ionian Sea; SION et al, 2004). As a matter of fact, the length by depth distribution pattern appears coherent with the 4 th hypothesis proposed by MORANTA et al (2004) to explain the biomass peak at intermediate level in the deep fish assemblages: G. melastomus lengths tend to increase up a maximum at intermediate depth level, thereafter tend to decrease. Since the youngest specimens occur almost exclusively in shallower depths, juveniles and adults share the upper and lower slope bottoms, and adults prevail at intermediate depth levels, the occurrence of slight pattern variation may explain the apparent contrasting findings of increasing (CARBONELL et al, 2003;REY et al, 2005;RINELLI et al, 2005; present study), stable (TURSI et al, 1993) or even decreasing (SION et al, 2004) local length by depth relationships.…”

“…Both past (CARRASS N et al, 1992;STEFANESCU et al, 1992) and recent (UNGARO et al, 2001;SARD et al, 2004b) deep waters bottom trawling or baited video camera (JONES et al, 2003) surveys in other Mediterranean basins clearly indicate G. melastomus as an important component of both upper and middle slopes fishing assemblages MORANTA et al, 2004) with an abundance peak at intermediate depth level (700-1000m;MORANTA et al, 2004).…”

“…Within the Mediterranean Sea, it is the main representative of the genus; the other valid (CASTILHO et al, 2007) Galeus species, the Saw tail catshark, Galeus atlanticus (Vaillant, 1882), being limited to the Alboran Sea (BAINO et al, 2001). In the Mediterranean Sea, the Blackmouth catshark occurs from the outer shelf edge (~150m) down to the boundaries between the middle (800-1400m) and lower (>1400m) slope bottoms, no matter the basin considered (GOLANI, 1986/87;STEFANESCU et al, 1992;RELINI et al, 1999;BAINO et al, 2001;JONES et al, 2003;SION et al, 2004;MORANTA et al, 2004;REY et al, 2005;CAPAPÉ et al, 2008). However, it is worth remarking on , the occasional intrusions at 50-60m (Southern coasts of France; DELATTRE & MAIGRET, 1986;CAMPILLO, 1992) and the photographic (baited camera) identification (although not confirmed by capture) of Galeus melastomus specimens between 2300 and 3850m (Eastern Mediterranean; JONES in PRIEDE & BAGLEY, 2000).…”

An introduction to Mediterranean deep-sea biology

“…In the deeper range the main catch families are composed of Moridae (Mora moro) and Alepocephalidae (Alepocephalus rostratus) of large size or Macruridae (Coelorhynchus coelorhynchus, Trachyrhynchus scabrus, Hymenocephalus italicus, Chalinura mediterranea, Nezumia aequalis) of medium size. High biomasses of these species are detected between 900 and 1300 m (Rucabado et al, 1991;Stefanescu et al, 1992;Morales-Nin et al, 2003;Massutí et al, 2004;Moranta, et al, 2004), but no fishery is carried out at the moment at these depths.…”

Reproductive characteristics of the bathyal viviparous fish <i>Cataetyx alleni</i> (Osteichthyes: Bythitidae) from the southeastern Sardinian Sea (central-western Mediterranean) MARIA

“…The species is distributed in the western basin [Catalan Sea between 984 and1851 m (Matallanas, 1983;Stefanescu et al, 1992), Balearic Islands between 700 and 1600 m (Moranta et al, 1998(Moranta et al, , 2004Morales-Nin, 2001), Ligurian Sea between 473 and 750 m (Relini Orsi, 1971, 1974Relini et al, 1986) and Sardinian Channel between 800 and 1420 m (Follesa et al, 2005(Follesa et al, , 2010], and in the eastern basin only in the southern Adriatic Sea between 1074 and 1196 m (Ungaro et al, 2001). Only a few specimens of C. alleni have been collected in the eastern North Atlantic (Porcupine Seabight) between 770 and 1205 m (Merrett et al, 1991).…”