Short spatio-temporal variations in the population dynamics and biology of the deep-water rose shrimp Parapenaeus longirostris (Decapoda: Crustacea) in the western Mediterranean

The deep-water rose shrimp Parapenaeus longirostris is a demersal decapod crustacean that is commercially exploited by trawl fleets. The present work compares its population dynamics, biology and condition in two locations (southern and north-western Mallorca in the Balearic Islands, western Mediterranean, separated by a distance of 120 km) with different environmental conditions and explores the relationships between the species and certain environmental factors. Six multidisciplinary bimonthly surveys were carried out during 2003 and 2004 in these two locations (between 150 and 750 m depth) in order to collect data on the demersal species with bottom trawl, the hydrography (temperature and salinity) with CTD casts, and trophic resources (zooplankton in the water column and suprabenthos with Bongo net and Macer-GIROQ sledge respectively) and sediments with a Shipeck dredge. The trawl fleets from both locations were monitored by monthly on board sampling and daily landings obtained from sales bills. Additional data was obtained from other trawl surveys. Temporal differences were detected both annually, with a decreasing trend over the last years in species abundance, and seasonally, in the biological indexes analysed. Bathymetric differences were also found in abundance, mean length, sex-ratio and condition of females. There were clear differences between the two locations studied, with higher abundance, condition and mean length and a lower length at first maturity for females in the north-western location. Trophic conditions could act as a link between geo-physical and biological changes. These short spatio-temporal differences could be due to the higher productivity found at this location, with higher density of preferred prey for the studied species together with adequate seafloor topography, sediment composition and hydrographical characteristicsPublicado

Condition and recruitment of Aristeus antennatus beyond fishing ground (to depths of 2200 m) in the Mediterranean: relationship with environmental factors

Depth relationships and seasonal trends in the biological condition and recruitment of the red shrimp Aristeus antennatus have been analyzed along down to 2300 m, over all the slope in the Balearic Basin (western Mediterranean). The analysis is based on a composite year (2008-2012 period) and identifies environmental causes of the trends. We found good reproductive and general biological condition of A. antennatus (Gonado-somatic index, GSI) at 800-1300 m in summer (June-July), depths below the fishing grounds. Mating and spawning were at depths below the more saline waters of the Levantine Intermediate water mass. Recruits Smallest juveniles (recruits, ca. 1 yr age) were exclusively distributed below 1000 m, associated with high near-bottom O2 concentration, low turbidity and high C/N in sediments implying favourable trophic conditions. A seasonal migratory pattern is suggested for females, which move shallower to the upper slope during periods of water-mass homogeneity (autumn-winter) to feed in canyons, increasing their energy reserves (hepatic gland weight, HSI). Females move downslope (800-1100 m) to spawn (high GSI) during periods of water mass stratification (late spring-summer). HSI of A. antennatus females decreased linearly with depth down the slope in February and in October-November, i.e., before and after the reproductive period. This nutritional condition of females in these periods is consistent with more consumption of benthic prey (ophiuroids, polychaetes, Calocaris macandreae) at the canyon heads (Cartes, 1994) in late autumn and winter. Our results confirm/suggest: i) how important it is to study the biology of deep-sea species over the whole depth range they inhabit and not only over fishing grounds, and ii) that changes in environmental conditions linked to the progressive warming of Mediterranean Deep Water (WMDW) with a parallel increase of salinity could provoke a decrease of O2 in water masses at below 1000 m, affecting A. antennatus recruitment and its life cycle, which is extensible to other deep-sea specie

Larvae of the blue crab Callinectes sapidus Rathbun, 1896 (Decapoda: Brachyura: Portunidae) in the Balearic Archipelago (NW Mediterranean Sea)

The invasive blue crab Callinectes sapidus has been frequently recorded during the last years along the NW Mediterranean Sea, leading to established populations. Two megalopae of C. sapidus were found during two different oceanographic surveys in open waters of the Balearic Archipelago, in July 2005 and October 2011, previous to the first reference of adult specimens documented in the Balearic sub-basin. The analyzed environmental conditions of the sampling periods allowed us to hypothesize the likely introduction pathways, namely by maritime transport and surface currents. Furthermore, the recorded megalopae seem to enlarge the life history of C. sapidus in regard to its native area, where spawning peaks occur in late July and early August.Versión del editor

Changes in the diet and feeding of the hake Merluccius merluccius at the shelf-break of the Balearic Islands: Influence of the mesopelagic-boundary community

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Condition and recruitment of Aristeus antennatus at great depths (to 2,300 m) in the Mediterranean: Relationship with environmental factors

Depth and seasonal trends in the biological condition and recruitment of the red shrimp (Aristeus antennatus) have been analyzed over the slope to 2,233 m in the western Mediterranean. The best biological condition of A. antennatus (gonadosomatic index [GSI]) for mating and spawning occurred at 800–1,300 m in summer, in areas deeper than the fishing grounds distributed between 500 and 800 m. Females moved shallower to feed on the upper slope during periods of water-mass homogeneity (autumn–winter), increasing their hepatic gland weight (hepatosomatic index [HSI]). Females moved downslope (800–1,100 m) to spawn (high GSI) during periods of water mass stratification (late spring–summer). The HSI of females decreased with depth down the slope in autumn, after the reproductive period. Small juveniles were distributed deeper than 1,000 m, associated with high near-bottom O2 levels, low turbidity and high C:N in sediments, implying favorable trophic conditions. This confirms the importance in studying the biology of deep-sea species over their entire depth range. The progressive warming and increasing salinity of deep Mediterranean waters could provoke a decrease of dissolved O2 that would affect the life cycle of A. antennatus2,04

Small-scale differences in the distribution and population dynamics of pandalid shrimps in the western Mediterranean in relation to environmental factors

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Isotopic composition of carbon and nitrogen of suprabenthic fauna in the NW Balearic Islands (western Mediterranean)

Dynamics of suprabenthos and zooplankton were analyzed in two areas located in the NW (off Sóller harbour) and S (off Cabrera Archipelago) of Mallorca (Balearic Islands, western Mediterranean) at depths ranging between 135–780 m. Four stations situated respectively at 150 m (shelf-slope break), and at bathyal depths of 350, 650 and 750 m were sampled at bi-monthly intervals during six cruises performed between August 2003 and June 2004. Suprabenthos showed maximum biomass in both areas from late spring to summer (April to August), while minimum biomass was found in autumn (September–November). Though variable, temporal dynamics of zooplankton showed peaks of biomass in late winter and summer (February and June), while minimals occurred in autumn (August–September) and, at bathyal depths, in April. Suprabenthos (abundance; MDS analyses) showed a sample aggregation as a function of depth (3 groups corresponding to the shelf-slope break, upper slope — over 350 m; and the middle, deeper part of the slope — over 650–750 m), without any separation of hauls by season. By contrast, zooplankton samples were separated by season and not by depth. There was evidence of three seasonal groups corresponding to summer (June 2004–August 2003), autumn–winter (September and November 2003, February 2004), and spring (April 2004), being especially well established off Sóller. In general, suprabenthos was significantly correlated with the sediment variables (e.g. total organic matter content (% OM), potential REDOX), whereas zooplankton was almost exclusively dependent on Chl a at the surface, which suggests two different food sources for suprabenthos and zooplankton. The increase of suprabenthos abundance in April–June was paralleled by a sharp increase (ca. 2.8 times) in the %OM on sediment during the same period, coupled ca. 1–2 months of delay with the peak of surface Chl a recorded in February–March (from satellite imagery data). Suprabenthos biomass was also correlated with salinity close to the bottom, suggesting a link between suprabenthos abundance and changes in the oceanographic condition of water masses close to the bottom. It is suggested that a higher suprabenthos biomass recorded off Sóller in comparison to that off Cabrera in June could, in turn, be related to a seasonal inflow of Levantine Intermediate Water (LIW) in April–June in this area at mid bathyal depths (350–650 m). This trend would be based on: 1) it was evident only at mid-slope depths between 350–750 m, coinciding with the LIW distribution, and 2) it was not recorded among zooplankton (collected throughout the water column). The possible effect of the fluctuations of suprabenthos and zooplankton on higher trophic levels has been explored studying the diet and food consumption rates of the red shrimp Aristeus antennatus, as indicator species by its dominance in bathyal communities. A. antennatus increased its food consumption from February to April–June 2004 off Sóller, which in the case of large (CL > 40 mm) specimens was found in both areas. In addition, there was a shift of diet from winter to spring–early summer. In this last period, A. antennatus preyed upon euphausiids and mesopelagic decapods and fish, while benthos (e.g. polychaetes and bivalves) decreased in the diet. This indicates an increase in the food consumption and probably in the caloric content of the diet in pre-spawning females in April–June 2004, which is synchronized with the period when gonad development begins in A. antennatus females (May–June). Anyway, macrozooplankton, and not suprabenthos, is crucial as a high energetic food source in the coupling between food intake and reproduction in the red shrimp

Near-bottom zooplankton over three seamounts in the east Canary Islands: Influence of environmental variables on distribution and composition.

The near-bottom zooplankton over three seamounts of the eastern Canary Islands (Amanay, El Banquete and Concepción) was analyzed, identifying the environmental variables that explain biomass distributions over them. Zooplankton composition changed between adjacent water masses, except for the two deepest assemblages associated with Atlantic Antarctic Intermediate Water (AAIW) and Mediterranean Water (MW). The highest biomass of total zooplankton and of main taxa (e.g. copepods, chaetognaths, siphonophores) were recorded at the seamount summits, i.e., over Amanay-El Banquete (summit depths of 23–24 m) associated with Surface Water (SF) and over Concepción (150 m) in upper levels of the North Atlantic Central Water (NACW). Biomass minima at the three banks were found at ca. 250–650 m, in the deepest levels of NACW. At ca. 700–1000 m (the level occupied by AAIW) and below 1000 m (MW level) biomass increased again. Near-bottom fluorometry (f5mab, 5 m above bottom) and dissolved oxygen (O2 5mab) were the main variables explaining changes of total zooplankton/main taxa biomass. Biomass minima (250–650 m) coincided with decreases of O2 5mab (3.30–3.99 ml/l at 400–700 m) at deepest depths occupied by NACW. Other variables not included in our models like turbidity (resuspension of particles) may have locally enhanced zooplankton aggregation, as they may locally occur alongside Concepcion at the NACW-AAIW confluence (at ca. 700 m), probably from the effects of internal waves. Our results suggest that observations regarding the attraction of organisms to the stationary substrates of seamounts could be related to elevated chlorophyll fluorescence and O2 5mab concentration. Peaks in those variables apparently enhance zooplankton aggregation

Long-term climatic influences on the physiological condition of the red shrimp Aristeus antennatus in the Western Mediterranean Sea

Changes in the physiological condition (represented by Kn = body weight/length predicted weight) of the deep-sea shrimp Aristeus antennatus associated with the warming and rising salinity trends in the western Mediterranean were analyzed to explore how deep-sea populations can reconfigure their biology to match the changes in ocean conditions. Two slope areas around the Balearic Islands (Western Mediterranean Sea) were analyzed using sampling data and generalized additive models. The 23 yr time series of monthly Kn estimates shows 2 different aspects of the life history of A. antennatus, corresponding to 2 different seasonal periods. The Kn series from June through September reflects the shrimps’ reproductive condition to the north of the Islands, while samples from October through May represent a period of low gonad weight and high hepatosomatic indices to the south of the Islands. Oceanographic variables used to construct models and seek relationships with changes in Kn were salinity, temperature, and dissolved oxygen in the Levantine Intermediate Water and Western Mediterranean Deep Water layers, and chlorophyll a satellite imagery data. The North Atlantic Oscillation and the Eastern Atlantic index were used as climatic indicators. Physiologic condition during the winter fattening periods decreased over the time series and was negatively correlated with increasing salinity. During the summer reproductive periods, the best-fitting models show a year-on-year effect and a significant probability of effects on condition from oligotrophication. These results suggest that increasing salinity at depth, which ultimately increases oligotrophy, may cause changes in physiological conditionVersión del editor1,99

Distribution and biogeographic trends of decapod assemblages from Galicia Bank (NE Atlantic) at depths between 700 to 1800 m, with connexions to regional water masses

The Galicia Bank (NE Atlantic, 42°67′N–11°74′W) is an isolated seamount, near NW Spain, a complex geomorphological and sedimentary structure that receives influences from contrasting water masses of both northern and southern origins. Within the project INDEMARES, three cruises were performed on the bank in 2009 (Ecomarg0709), 2010 (BanGal0810) and 2011 (BanGal0811) all in July–August. Decapods and other macrobenthic crustaceans (eucarids and peracarids) were collected with different sampling systems, mainly beam trawls (BT, 10 mm of mesh size at codend) and a GOC73 otter trawl (20 mm mesh size). Sixty-seven species of decapod crustaceans, 6 euphausiids, 19 peracarids and 1 ostracod were collected at depths between 744 and 1808 m. We found two new species, one a member of the Chirostylidae, Uroptychus cartesi Baba & Macpherson, 2012, the other of the Petalophthalmidae (Mysida) Petalophthalmus sp. A, in addition to a number of new biogeographic species records for European or Iberian waters. An analysis of assemblages showed a generalized species renewal with depth, with different assemblages between 744 and ca. 1400 m (the seamount top assemblage, STA) and between ca. 1500 and 1800 m (the deep-slope assemblage over seamount flanks, DSA). These were respectively associated with Mediterranean outflow waters (MOW) and with Labrador Sea Water (LSW). Another significant factor separating different assemblages over the Galician Bank was the co-occurrence of corals (both colonies of hard corals such as Lophelia pertusa and Madrepora oculata and/or gorgonians) in hauls. Munidopsids (Munidopsis spp.), chirostylids (Uroptychus spp.), and the homolodromiid Dicranodromia mahieuxii formed a part of this coral-associated assemblage. Dominant species at the STA were the pandalid Plesionika martia (a shrimp of subtropical-southern distribution) and the crabs Bathynectes maravigna and Polybius henslowii, whereas dominant species in the DSA were of northern origin, the lithodid Neolithodes grimaldii and the crangonid Glyphocrangon longiristris, likely associated with LSW. The diversity (H and J) of small crustaceans (collected with BT) seemed to be controlled by the phytoplankton blooms (satellite Chl a data) over bank surface 3 months before the samplings, both at the top (Spearman r=0.57, p=0.03) and on the flanks (r=0.74, p=0.02) of Galicia Bank, while no significant relationships with Chl a were found for the larger decapods collected with GOC73, on average they feed at the higher trophic levels than those collected with BT.Publicado