Estimates of growth and longevity of six species of freshwater shrimps (Macrobrachium spp.) (Decapoda: Caridea: Palaemonidae) from Costa Rica

Abstract

Information about growth is of particular relevance for stock assessment and management as well as for evaluating the aquaculture potential of any decapod species, but this information is lacking for the Central American species of MacrobrachiumSpence Bate, 1868. We collected specimens of six species of Macrobrachium monthly (February 2006 to August 2008) along the Pacific slope of Costa Rica. The collected individuals were sexed and weighted, and total length (TL) and carapace length (CL) were measured. The von Bertalanffy growth model was fitted to the data by applying the maximum likelihood method. The species analyzed reaching theoretically the largest sizes were M. americanum (Spence Bate, 1868), M. tenellum (Smith, 1871), and M. panamenseRathbun, 1912. With few exceptions, maximum sizes of all species were generally higher than those published in previous reports, suggesting that environmental conditions are favorable and anthropogenic impacts may be less severe in Costa Rica than in other countries. Only M. americanum exceeded the asymptotic total length estimates of other species, corroborating that this species is considered as one of the largest congeners worldwide. Estimated maximum age ranged from 3.9 (M. occidentaleHolthuis, 1950) to 11.5 yrs (M. tenellum). All six Macrobrachium species showed a positive allometric growth type. The model describing the length-weight relationship was statistically significant (P < 0.05) for all species. Although the maximum likelihood method has been applied so far mainly to compare different growth models, here we used this method to generate the first growth estimates for the six species from Costa Rica, and future studies might use this method to compare growth patterns among different species.