Population structure of pond-raised Macrobrachium amazonicum with different stocking and harvesting strategies

The effect of size-grading of juveniles prior to stocking, as well as selective harvesting, on the population structure of pond-raised Macrobrachium amazonicum was studied. A randomized-complete-blocks design with 4 treatments and 3 replicates was used. The treatments were: upper size-graded juveniles, lower size-graded juveniles, ungraded juveniles (traditional), and ungraded juveniles with selective harvesting. Twelve 0.01 ha earthen ponds were stocked at 40 juveniles m(-2), according to the relevant treatment. Every three weeks, random samples from each pond were obtained for biometry, and after 3.5 months, the ponds were drained and completely harvested. Animals were then counted, weighed, and sexed; males were sorted as Translucent Claw (TC), Cinnamon Claw (CC), Green Claw 1 (GC1), and Green Claw 2 (GC2), and females as Virgin (VF), Berried (BE), and Open (OF). The prawns developed rapidly in the ponds. attaining maturity and differentiating into male morphotypes after about 2 months in all treatments. The fast-growing juveniles (upper grading fraction) mostly did not constitute the dominant males (CC] and GC2) in the adult population. Population development was slower in ponds stocked with Lower prawns, whereas selective harvesting increased the frequency of GC1 and reduced the final mean weight of GC2 males. The proportion of males increased throughout the culture period, but was generally not affected by the stocking or harvesting strategies. Grading juveniles and selective harvesting slightly altered the population dynamics and structure, although the general population development showed similar patterns in ponds stocked with upper, lower, and ungraded juveniles, or selectively harvested. (C) 2010 Elsevier B.V. All rights reserved.

Population structure and sexual maturity of the calico box crab Hepatus epheliticus Linnaeus (Brachyura, Hepatidae) from Yucatan Peninsula, Mexico

The calico box crab Hepatus epheliticus is an abundant species from shallow and continental shelf waters of the Atlantic coast of USA and Mexico. Information about population structure and sexual maturity is absent, even though this crab is caught to be used as bait for the octopus fishery in the Campeche Bank, Mexico. In order to achieve such information, a total of 768 individuals were collected from January to March 2010 through baited traps installed in the Yucatan Peninsula, Mexico. Our results showed that sex ratio is biased towards more males than females (1:0.55), contradicting to that reported in other brachyuran crabs. The absence of ovigerous females suggests that they did not enter into the traps during embryogenesis. Males reached a larger maximum size than females (64.0 +/- 6.15 and 58.4 +/- 5.60 mm carapace width, respectively). The general scheme of growth being positive allometric throughout ontogeny of both sexes. Males presented a transition phase from juveniles to adult corresponding to the puberty moult. The estimation of the onset of functional sexual maturity revealed a steady situation for the population, with 21.5 and 13.8% of males and females, respectively, morphologically immature at the time of catch. This study constitutes the first report on population structure and sexual maturity in a population of the calico box crab H. epheliticus.