Ramón Muiño

Size at maturity of Liocarcinus depurator (Brachyura: Portunidae): a reproductive and morphometric study

Sexual maturity in brachyurans is often associated with an allometric change in the relative growth of the animal. Maturity of Liocarcinus depurator was examined by analysing the monthly percentages of mature females (determined by the stage of gonad maturation and the presence of brood and sperm plugs) by size-class and the relative growth of different body parts: length and width of the carapace, length, height and width of the cheliped propodus; width of the abdominal segments in females and length of the first pleopod in males. Using the reproductive criteria the size at the onset of sexual maturity (carapace width at which 50% females are mature) in females of L. depurator is around 30–34 mm cephalothorax width. Principal component analysis (PCA) showed that the main source of morphometric variation for both sexes was due to heterochelia and allometric changes in growth. Morphometric variables were fitted using different regression techniques to one and two-phase growth models. The length of the first pleopod and the propodus of the right cheliped in males, and width of abdominal segments in females showed two clearly differentiated phases. Estimated maturity size (carapace width) corresponding to 50% mature animals was greater in males than in females. In males, size at the onset of maturity ranged between 31.4 and 35.7 mm, depending on the methods and variables used. The size at the onset of maturity in females ranged between 25.5 and 31.5 mm. In the Ria de Arousa, the size at maturity in females of L. depurator estimated using reproductive criteria is considerably greater than the size found based on morphometric criteria. The size at maturity based on morphometric criteria is greater in males than in females.

The characterization of sardine (Sardina pilchardus Walbaum) schools off the Spanish-Atlantic coast

This paper describes the main characteristics of sardine schools detected in the SpanishAtlantic surveys carried out from 1992 to 1997 (except 1994). A series of parameters were obtained for each school (morphological, positional and energetic) as well as environmental factors (temperature and salinity). The relationships between the school parameters were analyzed by a PCA and then the school parameters per se were described using both univariate and multivariate analyses (Box-plots, ANOVAs, MANOVA, and discriminant analysis). The results show that significant differences exist between years and geographic

Fecundity of Liocarcinus depurator (Brachyura: Portunidae) in the Ría de Arousa (Galicia, north-west Spain)

The fecundity of Liocarcinus depurator (Decapoda: Brachyura) in the Ria de Arousa (Galicia, north-west Spain) and the reasons why it fluctuates were analysed, comparing the results with data available from other geographical areas. The incubation of L. depurator eggs in the Ria de Arousa generally takes place between January and September, although ovigerous females can be found all year round. The number of eggs per brood in L. depurator varied considerably in the Ria de Arousa and ranged from 5265 (carapace width (CW=31·3 mm, stage III) to 203,724 (CW=44·6 mm, stage I). The allometric equations adjusted to fit each egg development stage indicated that there was a strong positive correlation between female body size and the number of eggs the animal is able to bear. Female body size, measured as the carapace width, was the main factor causing variability in the fecundity of L. depurator . The second most important cause of variability in the development stages of the eggs was the number of eggs per brood, which may be due to the gradual loss of eggs that occurred during the incubation of these eggs in the female abdomen. Temporal changes constituted another significant factor in the variability of the fecundity of L. depurator . The allometric equations (log F=log a+b×log CW) fitted to each month and development stage I presented changes in the slope which point to the existence of a temporal evolution in the number of eggs. In the Ria de Arousa and for all the development stages, L. depurator was found to have a significant negative correlation between the number of eggs per clutch and egg volume. Egg volume also correlated negatively with the size of the female in stages I of the egg development. The degree of correlation between the volume and number of eggs was greater than the correlation between volume and size. The main cause of the variability in the egg volume of L. depurator in the Ria de Arousa may be attributed to the development stage (ANCOVA, P

Modelling the distribution and density of the invasive seaweed Sargassum muticum (Fucales, Sargassaceae) in shallow subtidal areas

The present study describes the distribution and density of Sargassum muticum in shallow subtidal areas of the Marine Fishery Reserve (MFR) ‘Os Minarzos’ (Galicia, north-western Spain) by using a data-collection strategy and a statistical approach fairly unused in literature. Our surveys showed a rapid spread of the invasive alga in the study area, where the number of patches increased more than 50% between 2008 and 2009. A model-selection approach was used to test the goodness of fit of Sargassum density data and the zero-inflated Poisson (ZIP) appeared to be the best model. The ZIP model quantified a probability of 22% of finding at least one Sargassum plant in a randomly placed quadrat within 11-m depth, demonstrating that a large part of the MFR has been invaded. In particular, the ZIP model showed that season, richness of macroalgal community, and abiotic factors, such as wave exposure and depth, are essential drivers for the establishment of S. muticum thalli in subtidal areas. Our results showed that the invasion of subtidal areas often follows patterns similar to the intertidal areas. The present study also demonstrated the usefulness of zero-inflated models to assess early and mid-stages of a seaweed invasion.

Fecundity of Liocarcinus arcuatus (Decapoda: Brachyura) in the ria de arousa (Galicia, NW Spain)

Abstract The fecundity and the possible causes of its variability were analyzed in the crab Liocarcinus arcuatus from three different areas of the Ria de Arousa (Galicia, NW Spain). The number of eggs per brood that a female is capable of carrying varied considerably, ranging from 889 to 134525 eggs. Body size was the main source of variability in number of eggs per brood. The second most important cause of the variability in egg number per brood was different in the spatial (the cause was the station itself) and the temporal (month and egg stage explained similar variance) ANCOVAs of all egg stages. Also spatial and temporal variation had a significant influence (P<0.001) on fecundity. Monthly relationships between carapace width and number of eggs per brood was calculated in each sampling station and there was a significant (P<0.05) strong positive correlation between carapace width and number of eggs, with slopes ranging, in most cases, from 2.5 to 4.8. In all the sampling stations and for the three developmental stages of the eggs, a significant negative correlation (P<0.05) was found between the number of eggs per brood and egg volume, similar to the correlation between the latter and body size. Significant spatial or temporal differences were observed mainly to eggs developmental stage I (ANCOVA, p<0.001).