Biology

Information about reproductive biology is significantly needed in management of blue swimming crab (Portunus pelagicus) fishery. This research informs spatial and temporal sex ratio, gonadal development, gonado somatic index (GSI) and first size sexual maturity of male and female crab, as well as crab spawning season in Lasongko Bay, Southeast Sulawesi. Crab collection were conducted with gillnet in five different types of habitat. Gonadal development of crab was examined by their color and morphological characters. Sex ratio was analyzed of χ 2 test, and gonadal development proportion of male and female crabs were described. Gonado somatic index (GSI) among stations were analyzed by one-way ANOVA and followed by Tukey's test. Sex ratio of crabs spatially and temporally of generally did not differ significantly from 1:1. Gonad developments of male and female crab were varied spatially and temporally. GSI at every gonad development stage of male and female crabs generally was not significantly different among stations. GSI of male crab was smaller than the female crab. The first sexual maturity size of male and female crabs were 109.8 mm carapace width (CW) and 115.7 mm CW, respectively. The crab spawned in Lasongko Bay the whole year, and three peaks of spawning season were detected.

Blue swimming crabs (BSC) (Portunus pelagicus) fisheries in Southeast Sulawesi waters have experiencing huge pressure, however studies on their reproductive biology were limited. The objective of the study was to find out the growth model, size at the first maturity, fecundity, and sex ratio disparity of BSC. The samples were collected monthly during June 2014 - April 2015 using gillnets, crab pots or hand-picking. Berried females were collected for fecundity (F) analysis. Relationship between weight (W) and carapace width (CW) were analyzed using a simple linear regression. The CW size of the first maturity was pointed out at 50% of frequency cumulative (CW₅₀), while relationship between F and CW was analyzed following F = a*CW^_b. Sex ratio of both sexes was tested using the Chi-square (α = 0.05). The result shows growth model of both sexes was “allometric” (b < 3) following equation of W = -1.6181 + 0.0224*CW for males and W = -1.7909 + 0.0238*CW for female. The relationship between F and CW was F = 80.443e^0.0236 CW (r = 0.7679). This organism produces high fecundity as its biology reproductive strategy to maintain its population. Males and females attaine the first maturity at CW₅₀ of 11.957 cm and 10.802 cm, respectively. The sex ratio generally females preponderate over males, however, the Chi-square test was not significantly different. Factors affecting sex ratio disparity were mainly locations (water quality), migration and distribution patterns according to sex, sampling method, gears catchability, mortality and growth, reproduction activities, and CW sizes.

Ernawati T, Sumiono B, Madduppa H. 2017. Reproductive ecology, spawning potential, and breeding season of blue swimming crab (Portunidae: Portunus pelagicus) in Java Sea, Indonesia. Biodiversitas 18: 1705-1713. The blue swimming crab (Portunidae: Portunus pelagicus) is one of the most economically important fisheries species in Indonesia. Little is known about their reproductive ecology and key biological characteristics. This study aimed to investigate population biology and reproductive ecology (Carapace’s width to weight relationship, growth, natural mortality, size at first maturity and at first captured, Spawning Potential Ratio (SPR), and breeding season) of P. pelagicus at six important landing sites around the Java Sea (Jakarta, Cirebon, Demak, Rembang, Sumenep, and Sampit) from January 2014 to January 2015. Monthly data were collected by fishers at each landing sites, with a total of 14,408 individuals being measured. The study found that males were heavier than females and the smallest mean of individuals’ height belonged to Jakarta compared to other locations. The growth parameters varied at the different locations. Crabs could grow up to 100 mm in 10 months with the maximum age being less than three years. The growth rate (K) of more than 1 indicated a fast-growing crustacean with a short lifespan. The lowest carapace width at first capture (L c ) for the BSC was obtained from crabs caught using a bottom gillnet landed in Jakarta, followed by dredged crabs in Cirebon. The mean carapace width at first maturity (L m ) in the Java Sea was 10.6 cm, with the lowest L m of female crabs being landed in Cirebon and the highest in Sampit. The Spawning Potential Ratio (SPR) ranged from 11% to 24% and the selectivity curve for the BSC fishery at each landing sites is positioned well to the right of the generic maturity curve, except in Demak, suggests that the operation enables almost all crabs to mature and spawn before entering the fishery. The collapsible trap was the most selective gear, with an average catch of 112 mm across at all landing sites, and the least selective was in trawls. Therefore consideration needs to be given to the different gear types used to catch crabs to leave smaller crabs in the water longer to grow to maturity. Considering its fast growth and peak season (February-April and August-October), a short-period is recommended at some sites that have been over-exploited to rebuild a broodstock to support the long-term sustainability of this species.

An experiment was conducted to determine the effects of temperature on survival rate and larval development of blue swimming crab, Portunus pelagicus (Linnaeus, 1758) under cultured conditions. Five different constant temperatures (26, 28, 30, 32 and 34 ^oC) were compared in triplicate. The larval were fed a live diet and examined and daily and death or molts recorded. The result showed that survival rate and larval development were significantly different among treatments due to temperature (P< 0.05). ). The highest and lowest larval survival rates until C1 stages were promoted by 30 ^oC (36.67 %) and 34 ^oC (12.22 %). The second best survival rate of C1 (31.11 %) was obtained at 28 ^oC. The lowest larval development (3.67 - 4.00 days) occurred at 30-34 ^oC (P> 0.05). At 26 ^oC and 28oC larval development of C1 took around 5.67 days (P>0.05).

Kembaren DD, Zairion, Kamal MM, Wardiatno Y. 2018. Abundance and spatial distribution of blue swimming crab (Portunus pelagicus) larvae during east monsoon in the East Lampung waters, Indonesia. Biodiversitas 19: 1326-1333. The blue swimming crab/BSC, Portunus pelagicus, is an economically important species in fishery industry and continuously being exploited, particularly in the East Lampung waters. BSC research in Indonesia during the last decade was only restricted to the adult phase, while research on their larval dynamics in nature has not been done yet. This study aimed to assess the abundance and the distribution of BSC larvae, and to describe their correlation to its environmental conditions. This study was conducted in June 2017 (during east monsoon) in the East Lampung waters. Sampling was done in surface water during the daylight hours on nine sites with three replicates on each site. Plankton abundance and oceanographic profile were also recorded from the same sampling site. The result from this study showed that the water quality from the environment was suitable for the development of BSC larvae. The abundance of the early-stage larvae (Z1-Z3) was relatively higher than the late-stage larvae (Z4 and M). The larval stages of BSC were dispersed and completed their development in the mid-shore and offshore waters. There was a tendency that the early-stage was more abundant in the northern part, while the late-stage was more abundant in the southern part of the study area. The highest larval abundance was found in the mid-shore, particularly in site number five, which was influenced by the water mass density and current direction during the east monsoon. Moreover, oxygen concentration and salinity of the water environment influenced the early-stage larvae abundance more than the late-stages abundance.