Factors affecting Oithona nana and Oithona similis along a salinity gradient

Spatial and temporal variations of reproduction variables of the two cyclopoid copepods Oithona nana Giesbrecht, 1893 and Oithona similis Claus, 1866 were evaluated monthly from September 2007 to August 2008 in four ponds at different salinities in the solar saltern of Sfax, Tunisia, under hypersaline conditions. Along the salinity gradient the abundance of O. nana and O. similis declined from 14,900 ± 15,200 ind. m-3 (A1) to 6,800 ± 7,200 (C31) and from 13,800 ± 17,100 ind. m-3 (A1) to 3,700 ± 5,800 (C31), respectively. The findings showed that the abundance of these Oithona species, particularly the ovigerous females, was positively correlated with the abundance of Diatomeae, and negatively correlated with salinity. The egg production rate (EPR), the egg diameter, the clutch size, as well as the cephalothorax length of mature females, were all negatively correlated with salinity and positively correlated with the abundance of Diatomeae. Along the existing salinity gradient, the EPR decreased from 4.7 ± 0.39 (A1) to 3.2 ± 0.13 (C31) eggs female-1 day-1 and from 5.19 ± 0.46 (A1) to 3.66 ± 0.05 (C31) eggs female-1 day-1 for O. nana and O. similis, respectively, and this could mainly be attributed to the hypersaline conditions. The positive relationship between the abundance of Diatomeae with all traits shows, that these may be a vital component of the diet for the investigated species. The reduction of body size of Oithona along the salinity gradient demonstrates that such a character could mainly be due to a network of causes, related with the confinement and not only to salinity.

Population dynamics and sustainability of the spiny lobster (Panulirus meripurpuratus Giraldes & Smyth, 2016) fishery on the Amazon continental shelf

The assessment of fishery resources is key to the development of management strategies for exploited stocks. Analysis of specific parameters provides information regarding the state of the stock and indicators of exploitation levels. The aim of the present study was to analyse the growth and mortality parameters, as well as investigate the exploitation status, of Panulirus meripurpuratus caught on the Amazon coast, northern Brazil. Growth parameters and stock assessment were estimated using R with bootstrapping and FISAT II, based on cephalothorax length–distribution frequency. Specimens were collected by the commercial lobster fishery off the coast of the states of Pará and Amapá between 2001 and 2002. The results indicate that the P. meripurpuratus stock assessed is composed of individuals with low growth rates and high estimates of maximum asymptotic length, with relative longevity of 21.37 years. The exploitation rate was operating at near the maximum limit of sustainability in 2001 and 2002. This is the first estimate of the exploitation status of P. meripurpuratus on the Amazon coast. We strongly recommend new monitoring efforts and further studies to support the conservation and management of the spiny lobster stock.

REPRODUCTIVE BIOLOGY IN GREEN SPINY LOBSTER, PANULIRUS REGIUS (DE BRITO CAPELLO 1864), FROM THE PETITE COTE OF SENEGAL, WEST AFRICA

Green spiny lobster is one of the highest economically valued fisheries resources in Senegal. However, knowledge on this species are relatively old and insufficient. To realize this study on reproductive biology of Panulirusregius, sampling has been carried out between April and September 2017 from small-scale fisheries landed catches at the Petite Cote, Senegal. The length at first sexual maturity computed from the body allometric relationship according to the cephalothorax length (CL) was 67.95 mm in females and 67.51 mm in males. The CL at which 50% of the females were mature during the breeding season (CL50) was 94.50 mm. Individual fecundity was between 229,860 and 638,775 eggs depending on CL of individuals. In the catches surveyed, 64% of landed individuals had a total length (TL) less than 200 mm, which is the minimum landing length in accordance with the Senegalese fisheries law. This result indicates the difficulties to apply management measures relative to this fishery, which could compromise its sustainability in Senegalese Petite Cote.

Spatial structure of the pink shrimp Penaeus (Farfantepenaeus) notialis (Pérez Farfante, 1967) (Decapoda, Penaeidae) in the Colombian Caribbean: implications for fisheries management

The objective of this study was to assess the patterns in the spatial distribution, size structure, morphometric relationships, and relationships of biomass and size to sampling depth and distance to the coast of Penaeus notialis in the Colombian Caribbean. The biological data were collected on board a shrimp trawler. The females were larger and heavier than the males, which indicated distinct sexual dimorphism in body size. The cephalothorax length at 50% maturity in females was 26.49 mm, and in males, it was 15.13 mm. Relatively high biomass values were found in the southern zone of the study area at depths between 25.6 and 49.3 m and between 3.94 and 7.80 nmi (= 7.29-14.45 km) from the coast. We found a clear spatial structure of biomass and size in relation to depth, so that the fishing effort can be directed to the locations of the adult population.

MORPHOLOGICAL VARIABILITY AND SEXUAL DIMORPHISM OF NOBLE CRAYFISH Astacus astacus FROM THE BALKANA LAKE

This paper presents the information about morphological variability and sex dimorphism of the Noble crayfish (Astacus astacus) in the area of the Balkana Lake in Mrkonjic Grad. The crayfish were caught by hand made baited traps from October 9nd 2018. until May 31th 2019. A total of 58 crayfish were caught, of which 38 males and 20 females. The eight morphometric characteristics: body weight (W), body length (TBL), claw length (CLL), cephalothorax length (CFL), carapace width (CPW), abdomen length (ABL), rostrum length (ROL) and rostrum width (ROW) were measured, both in males and females. Also, the body condition was determined for all specimens. The results of morphometric characteristics partially matched into the already known range of variations. These data represent first ones for the observed area. The t-test showed that there were significant differences between the sexes in W, TBL, CLL, CFL and CPW which are explained by the emphasized sex dimorphism of the noble crayfish.

Morphological variability and sexual dimorphism of noble crayfish Astacus astacus from the Balkana Lake

This paper presents the information about morphological variability and sex dimorphism of the Noble crayfish (Astacus astacus) in the area of the Balkana Lake in Mrkonjic Grad. The crayfish were caught by hand made baited traps from October 9nd 2018. until May 31th 2019. A total of 58 crayfish were caught, of which 38 males and 20 females. The eight morphometric characteristics: body weight (W), body length (TBL), claw length (CLL), cephalothorax length (CFL), carapace width (CPW), abdomen length (ABL), rostrum length (ROL) and rostrum width (ROW) were measured, both in males and females. Also, the body condition was determined for all specimens. The results of morphometric characteristics partially matched into the already known range of variations. These data represent first ones for the observed area. The t-test showed that there were significant differences between the sexes in W, TBL, CLL, CFL and CPW which are explained by the emphasized sex dimorphism of the noble crayfish.

Descriptions of the first zoeas of ten xanthid crabs (Crustacea: Decapoda: Xanthoidea) from the Gulf of Aqaba, Red Sea

Ovigerous females of 10 species of xanthid crabs (Xanthidae MacLeay, 1838), from five subfamilies, namely, Pseudoliomera speciosa (Dana, 1852) (Actaeinae), Chlorodiella cytherea (Dana, 1852), Chl. laevissima (Dana, 1852), Chl. nigra (Forskål, 1775), Cyclodius granulosus (De Man, 1888) (Chlorodiellinae), Danielea noelensis (Ward, 1942) (Euxanthinae), Liomera rugata (H. Milne Edwards, 1834), Lio. tristis (Dana, 1852) (Liomerinae), Lachnopodus subacutus (Stimpson, 1858) and Leptodius sanguineus (H. Milne Edwards, 1834) (Xanthinae), were collected from the Gulf of Aqaba, and the zoea I obtained from them have been described herein. Six species, viz. Chl. cytherea, Chl. laevissima, Cyc. granulosus, Lio. rugata, Lio. tristis and Lep. sanguineus, are described for the first time, and Lac. subacutus and D. noelensis are re-described. Spinulations of dorsal and rostral spines of cephalothorax, length of rostral spine of cephalothorax to protopod of antenna, setations of antennule, ratio of antennal exopod to protopod and setations of exopod of antenna are important characters that distinguish xanthid larvae from their congeners and other closely related species at subfamilial levels.

Sex Ratio and Growth Pattern of Coconut Crabs Birgus latro (Crustacea, Decapoda, Cianobitidae) in North Moluccas Province, Indonesia

Coconut crab (Birgus latro) is a crustacean that has a large size until four kilograms. The study aimed to analyze sex ratio and growth pattern including the relationship of thorax length - body weight, thorax width - body weight and cephalothorax length plus rostrum - body weight in Daeo (Morotai Island), Laigoma (South Halmahera District) and Fitako (North Halmahera District). The sex ratio was determined using χ2 test and the growth pattern was tested by the b value through t test. The results showed sex ratio of 1: 0.9 in Daeo (n = 581), 1: 0.6 in Laigoma (n = 24), and 1: 2 in Fitako (n = 31). The relationship of thorax length, thorax width and cephalothorax length plus rostrum with body weight were strongly correlated (R2> 70%). The growth pattern of coconut crab in Daeo was negative allometric, while in Laigoma and Fitako were negative allometric and isometric.

Reproductive strategies of a population of a freshwater amphipod (Crustacea, Amhipoda, Hyalellidae) from southern Brazil

The aim of this study was to characterize the reproductive strategies of a population of Hyalella bonariensis from southern Brazil. Pairing success, reproductive period of males and females, fecundity, and body size at the onset of reproduction were evaluated. Animals were sampled four times (August 2012, October 2012, January 2013, and April 2013) with the 250 µm-mesh dip net during 20 minutes by only one person. In the field, precopulatory pairs and ovigerous females were individualized. In the laboratory, cephalothorax length (CL) were measured and eggs and juveniles were removed from the females' marsupium and counted. The mean CL of paired males and females was significantly higher than that of non-paired males and females. A sexual dimorphism in body size was observed in the population - both paired and non-paired males were larger than females. Probably larger males have a higher probability of losing females during precopulatory behavior. A significant correlation was observed between the size of paired males and females - larger males often paired with larger females and smaller males paired with smaller females (r = 0.81). The pairing success of males increased with body size and we can assume that males from all size classes are able to find mates. The pairing success of females was independent of body size - paired and non-paired females had similar mean CL. The reproductive success increased with body size in males and females, and was more evident in males. Females from the largest size classes had null reproductive success. The idea that larger females can produce more eggs but might have a lower probability of finding a mate than smaller females was corroborated by our results. Therefore, smaller females have higher pairing success because they are capable of mating with a higher percentage of males. The estimated mean fecundity of H. bonariensis was 17.4 (± 3.89) eggs/juveniles. Our results are similar to those of other species of Hyalella from Brazil.

Structure and population dynamics of the secondary burrower crayfish Procambarus acanthophorus from a tropical Mexican wetland

Catch size, sex ratio, structure and dynamics, as well as mortality, of a population of the secondary burrower crayfish Procambarus acanthophorus Villalobos, 1948, from tropical wetland La Mixtequilla, Veracruz, Mexico, were examined. Monthly samples were taken from artisanal commercial captures. A total of 2141 individuals were caught. Although the total female:male ratio was 0.86, variation in sex ratios have also been found in monthly catches. Monthly polymodal frequency distributions of cephalothorax length (CL) were analyzed by the Bhattacharya method. Population catches consisted of six CL classes. The CL-class dynamic may show adaptations to the flood period. Growth parameters were estimated using the von Bertalanffy model. For females, K = 0.39 year−1, CL∞ = 57.30 mm, [Formula: see text] = 3.11, and tmax = 6.73 years were found; it is appropriate that for males, K = 0.40 year−1, CL∞ = 59.00 mm, [Formula: see text] = 3.14, and tmax = 6.59 years were found. We also examined whether water temperature influences the catches or sex ratio.