Spatial distribution patterns of the striped venus clam (Chamelea gallina, L. 1758) natural beds in the Gulf of Cádiz (SW Spain)

VENUSEstudio integral de los bancos naturales de moluscos bivalvos en el Golfo de Cádiz para su gestión sostenible y la conservación de sus hábitats asociado

Spatial distribution and community structure of megabenthic bivalves in the subtidal area of the Gulf of Cádiz (SW Spain)

VENUSEstudio integral de los bancos naturales de moluscos bivalvos en el Golfo de Cádiz para su gestión sostenible y la conservación de sus hábitats asociado

Investigación y gestión pesquera como elementos clave para alcanzar la sostenibilidad de la pesquería de chirla Chamelea gallina (Linnaeus, 1758) en las aguas españolas del Golfo de Cádiz

Fondos FEMP Andalucí

Workshop on the production of abundance estimates for sensitive species (WKABSENS). ICES Scientific Reports, 3:96.

The Workshop on the production of annual estimates of abundance of sensitive species (WKABSENS) met to define sensitive species, collate ICES assessments of abundance where these are available, and estimate indices of their abundance per swept-area where not, for the OSPAR area. The analyses identified 140 potentially sensitive species or species complexes, among which 10 are diadromous and three are coastal, 20 have uncertain species ID and nine were identified as sensitive in only one of the sources examined. Among the sensitive species and species complexes, there was sufficient data to provide abundance indices for 50 species, of which 16 had existing stock assessments whereas the workshop derived abundance estimates for the remaining 34 species from survey data. Three statistical modelling approaches (binomial, General Additive Models (GAMs) and VAST) and were explored and the final abundance indices were calculated using GAMs. The species were divided into stocks before estimating abundance indices where these could be identified from the spatial distribution of the species in the survey. The group considered that a similar analysis using data from additional surveys, commercial indices or data from bycatch observers can potentially provide improved abundance estimates for species with variable or low catchability, such as deep-water and pelagic species

Abundance prediction and influence of environmental parameters in the abundance of Octopus (Octopus vulgaris Cuvier, 1797) in the Gulf of Cadiz

10 pages, 7 figures, 2 tablesUnderstanding the processes that influence octopus abundance is important in order to manage the fishing grounds and offer advice on the exploitation of this important resource. Fluctuations in abundance of exploited stocks may be due to a great variety of factors. However, in short-lived animals such as cephalopods, in which abundance depends on strength of the recruitment, it is well known that population abundance is highly influenced by the environmental conditions. In this study we investigated the relationship between octopus (Octopus vulgaris) catches from the fishery located in the area off the Gulf of Cadiz (Spanish South Atlantic Region) and several hydrographic and oceanographic parameters such as sea surface temperature, surface chlorophyll-a, inorganic surface turbidity and climatic indicators such as the NAO index, rain, WeMoi Index, AMO index and or Guadalquivir River discharges. In addition, a recruitment index was obtained from fishery-independent surveys, which was also used to investigate its effect on annual catches. Results revealed that abundance of octopus showed a significant negative relationship with rain in the previous year as well as a positive effect of the recruitment index. We have obtained a model using the rain and the recruit index to forecast the catches. This model explained a high percentage of variation in annual catches and was used to forecast the next year’s catch providing results within the expected confidence intervals. This represents a potentially useful tool to guide fishery managers since no assessment of the species is currently conducted in the areaThis work was supported by the Research Program of Andalucia, Spain (project number RNM 1953) and the mobility program “Salvador Madariaga” of National Research program of Spain (grant numbers PRX16/00001)Peer reviewe

Descripción de la fauna macrobentónica en la zona intermareal del litoral de Huelva donde se desarrolla la pesquería de la coquina (DOnax trunculus Linnaeus, 1758)

This study reports the benthic megafauna that inhabit the coast of Huelva where the wedge clam fishery is carried out with hand dredges. Samples were collected seasonally using a specially designed hand dredge similar to that used by local fishermen but with a smaller mesh size bag (3 mm x 3mm). 35 georeferenced transects were performed using a GPS device to standardize data to swept area. A total of 45918 individuals with a biomass of 52799 g were obtained. An inventory of 32 species belonging to 5 phyla was identified from February to November 2014 in these fishing areas. In relation to the number of species and biomass, the Mollusca phylum was the most abundant group followed by Arthropoda. The most dominant bivalve mollusc was Donax trunculus (84%), followed by Mactra stultorum and M. glauca. The frequency index of D. trunculus was 100% for each season, and maximum values of abundance and biomass were observed in spring and summer.Versión del edito

Estructura poblacional, crecimiento y producción de la coquina Donax trunculus en la zona intermareal del litoral of Huelva

Population structure, growth and production of the wedge clam Donax trunclus, inhabiting highly exposed sandy beaches of the littoral of Huelva (SW Spain) were investigated between January 2014 and July 2015. Growth rates were estimated comparing two different methods in the intertidal zones of beaches: (i) length-frequency distributions (LFD) analysis in two separated beaches (Doñana and Isla Canela) (ii) internal shell growth bands by thin shell cross sections (TS). For the TS methodology, valves were embedded in methyl-methacrylate, and sequential sections were grounded and polished to a thickness of 80-100 µm. This technique allowed the identification of annual ring depositions and the shell length-age keys were performed. In addition, several deformities (related to environmental stress or damages probably caused by fishing gears) as well as signs or recovery were observed. Both methodologies were equally appropriate to estimate growth of D. trunculus. Von Bertalanffy growth functions were established from LFD and TS using an asymptotic length (L∞) of 44.8 mm and the growth constants (K) of 0.5 (LF) and 0.44 yr-1 (TS). The intertidal biomass of D. trunculus ranged between 3.03-3.31 g ash-free dry mass (AFDW) m-2 yr-1. Individual production revealed the highest value at 27 mm length (0.117 g AFDW m-2 yr-1) and annual production ranged between 3.40 and 4.91g, resulting in renewal rate values (P/B) between 1.03 y 1.61. Differences between beaches in terms of annual production and P/B seem to be partially related to human activities.Versión del edito

First insights into population parameters and spatial distribution of the two morphotypes of Mactra stultorum (brownish and whitish) (Linnaeus, 1758) (Mollusca: Bivalvia) along the southwestern Spanish coast

The aim of this study was to address an analysis of spatial distribution, reproduction, population parameters and secondary production of the natural beds of the well-defined morphotypes of the clam Mactra stultorum (brownish and whitish variants) along the SW Spanish coast. The main findings showed that the presence and the frequencies of both morphotypes increased near the estuaries of rivers, particularly the Guadalquivir River. However, subtle differences in habitat preferences have been revealed and the brownish variant showed a wider and deeper distribution. High similarity in the gonadal development was recorded for both variants. It started in January, continued into late winter and early spring and ended with a spawning period from April to August. An energy storage-utilization cycle, coupled to the reproductive and resting periods and driven by sea water temperature variations and food availability, was also observed. The abovementioned period of gamete emissions resulted in a recruitment pattern with a one-time settlement period per year. Von Bertalanffy growth functions provided an asymptotic length of 46.7 mm (whitish) and 50 mm (brownish) and growth constants of 0.55 (whitish) and 0.50 yr−1 (brownish). The mean annual biomass (B ̅) ranged between 0.062 (whitish) and 0.076 g AFDW m−2 yr−1 (brownish) (AFDW: ash-free dry mass). Individual somatic production showed the highest value at 32 and 34 mm shell length, and annual production (P) ranged between 0.075 and 0.113 g AFDW m−2 yr−1, resulting in renewal rate (P/B ̅) values between 1.21 and 1.37, for the whitish and brownish variants, respectively. These results provide basic knowledge about the reproduction and population dynamics of this species along the Atlantic coast, particularly in the sandflats near the estuary of the Guadalquivir River. They could also shed additional light upon taxonomic differentiation and clarify the ecological role of both variants when compared with two bivalve sympatric species of the intertidal and subtidal areas.Versión del editor1,48