Summer decapod crustacean larval communities along the eastern Spanish Mediterranean coast

Abstract

Decapod crustaceans are a diverse group englobing several species of commercial and ecological interest. In the Mediterranean Sea, decapod crustacean fisheries are among the most profitable, although in many cases their early life stages are poorly known. In this study, we tackle the composition and diversity patterns of the decapod larval communities along the eastern Spanish Mediterranean coast. Zooplankton sampling was carried out in surface waters at 101 stations from July 20th to August 31st 2016, over bottom depths between 90 and 1840 m. All shrimp larvae were identified to the lowest possible taxonomical level, and larvae from Anomura, Achelata and Brachyura were left at infraorder level. No larvae of Astacidea or Polychelida were found. The total zooplankton volume was estimated. A total of 20,022 decapod crustacean larvae were identified, focusing on shrimp taxa (suborder Dendrobranchiata and infraorder Caridea). Both zooplankton volume and decapod larval density values were higher in the northern part of the studied area, cut by deep submarine canyons. After assessing the diversity parameters of the decapod larval community, we present the summer mesoscale larval distribution of several species of commercial interest such as the caramote prawn (Penaeus kerathurus) or the deep-water rose shrimp (Parapenaeus longirostris). The northern submarine canyons are dominated by the presence of Penaeoidea, being the deep-sea shrimp Aristeus antennatus the dominant species in the community in this area, while the Sergestoidea are more abundant in the southern zone. This is the largest-scale study on decapod larvae mesoscale distribution in the Mediterranean Sea.

Fig 1. Division of GSA 6 in three zones (Northern, Central and Southern) according to references in the literature [35, 36].

Black dots represent stations sampled with neuston sledge.

Fig 2

A: Zooplankton volume estimation in samples (mL per 1000 m³ water filtered); B: Total decapod larval density (individuals per 1000 m³ water filtered).

Fig 3. Average relative larval density (in individuals per 1000 m³) of taxa in the 3 zones studied.

Fig 4. First quartile, median, third quartile and standard error for total decapod larval density (log (individuals per 1000 m³ + 1)), Zooplankton estimated volume (mL per 1000 m³), Shannon diversity index (H) and species richness (S) for the three zones of GSA 6.

Fig 5. Larval density in log10 (individuals 1000 m^-3 + 1) for the most abundant and/or frequent taxa of no commercial interest.

A: Sycionia carinata, B: Sergestidae; C: Alpheus glaber; D: Athanas nitescens; E: Lysmata spp.; F: Processa spp.; and G: Upogebia spp.

Fig 6. Larval density in log (individuals 1000 m^-3 + 1) for taxa of commercial interest.

A: Aristeus antennatus; B: Parapenaeus longirostris; C: Penaeus kerathurus; D: Plesionika spp.; and E: lobsters (Achelata).

Fig 7

NMDS species ordination over contours, representing environmental gradients for A: sea surface temperature (ºC), B: sea surface salinity (PSU), C: sea surface fluorescence (μg/L). ariant: Aristeus antennatus; parlon: Parapenaeus longirostris; penker: Penaeus kerathurus; siccar: Sicyonia carinata; alpgla: Alpheus glaber; athnit: Athanas nitescens.