Relationships between macro‐epibenthic communities and fish on the shelf grounds of the western Mediterranean

Abstract

ABSTRACT1. The present study characterizes the macro-epibenthic assemblages, and the relationships between demersal species and benthic habitats on the shelf trawl fishing grounds off the Balearic Islands (western Mediterranean).2. The data used were collected during experimental bottom trawl surveys from 2002 to 2005. A total of 157 samples from 38-255 m depth were analysed.3. Three macro-epibenthic assemblages were identified in both the shallow (at 38-91 m) and deep shelf (90-255 m). Macroalgae bathymetric distribution was identified as the main factor explaining the segregation between shallow and deep shelf assemblages.4. Two especially sensitive habitats were identified: mae¨rl and crinoid beds; a third habitat was identified as Peyssonnelia beds, which represented the highest biomass on the whole shelf, with a similar species richness to the mae¨rl beds. On the deep shelf, crinoid beds represented the highest biomass.5. Habitat type had a significant effect on the distribution of demersal commercial species, most of them being more abundant in the two sensitive habitats mentioned and in the Peyssonnelia beds. Some species showed sizespecific habitat preferences.6. Fisheries management in the area should take into account the resilience of these benthic habitats, and their importance from both ecological and sustainable fisheries management perspectives.

Feeding ecology of demersal elasmobranchs from the shelf and slope off the Balearic Sea (western Mediterranean)

“…With the only exception of S. canicula from the CS, which showed the most generalist diet (0.67), and G. melastomus from the US, which showed the most specialist behaviour (0.17), all other species had niche breadth values between 0.26 and 0.49 that might be associated with moderate levels of specialization. Such moderate levels could be related to the high species richness and biomasses of shelf benthic ecosystems from the Balearic Islands (Massutí and Reñones, 2005;Ordines and Massutí, 2009). Lower niche breadths on the slope than on the shelf might also be related to the already mentioned decrease in trophic resources with depth.…”

Inter- and intra-annual trends and status indicators of nektobenthic elasmobranchs off the Balearic Islands (northwestern Mediterranean)

“…Walker (1998) pointed out that certain shark fisheries are advantageous as they can produce relatively stable yields which are less prone to interannual environmental effects compared to the fisheries of most teleost stocks. The heterogeneity of bottoms, their sediment type and the widespread occurrence of sensitive and essential fish habitats in the Balearic Islands (Ordines and Massutí 2009) are possible explanations for the higher values of abundance, biomass, species richness and diversity compared to the waters off the Algerian coast . Biogeographic factors could be the basis of the above mentioned differences between the Balearic Islands and the Iberian Peninsula (Massutí and Moranta 2003).…”

Balearic Islands vs Algeria: two nearby western Mediterranean elasmobranch assemblages with different oceanographic scenarios and fishing histories

“…On the one hand, the higher values detected on the shelf and shelfbreak off the Balearic Islands than off Algeria could be explained by the heterogeneity of bottoms, their sediment type and the widespread presence of sensitive and essential fish habitats in the former area (e.g. soft red algae, maërl and crinoids beds; Ordines and Massutí, 2009). The heterogeneity of the seabed has been considered as an important factor that enhances the diversity of demersal fish species (Rogers et al, 1999).…”