Biometric and ecological study of the river shrimp (Macrobrachium genus) in the lower part of the Kukra river basin

Abstract

The Macrobrachium Gender made up of more than 100 species, of which 26 belong to the american continent (Pascual, 2005), they commonly known as river shrimp and/or prawn. Due to his trascendency like fishing resource they are considered of great economic importance, principally Macrobrachium carcinus and M. acanthurus, which are well known and exploited in the majority of the riverside communities throughout Latin America (García-Guerrero et al., 2013).
During the period of study (2006-2007), a total of 1180 specimen were captured, of Macrobrachium acanthurus 447 individuals were captured, 622 of M. carcinus and 111 of M. olfersii. All the captures were done with fishnets of bamboo of the Guadua specie of the Amplexifolia type that is the native one of Nicaragua.
During the study the average temperature was 27.2 ± 1.25 °C (range: 25 - 29 °C), average transparency of 0.3 ± 0.17 m (range: 0.26 – 0.45 m) and the average depth of 3 ± 0,25 m (range: 2 -4.5 m). In the sexual proportion (female: male) there was dominance of males, for M. carcinus the proportion was (1H: 0.9M) with a value of χ2 = 2.57 without significant difference, M. acanthurus presented a proportion of (1H: 1.66M) with a value of χ2 = 18.53 with significant difference and M. olfersii presented a proportion of (1H: 0.8M) whit a value of χ2 = 0.73 without significant difference. There is a significant difference when (χ2 < 3.84 and p > 0.05) (Vazzoler, 1996). M. carcinus presented an average Total Length (LT) of 15.8 ± 4.5 cm (range: 3.6 - 24 cm) and a Total Weight (W) of 105.4 ± 82.5 g (range: 1.7 - 382 g). For the three species, the model that best fits the growth of the population is the polynomial model, in M. carcinus (W = 1.6 LT2 - 28.2 LT + 118.6) it explains more than 90% of the relationship between W and LT (R2 = 0.9046). M. acanthurus presented average LT of 11.7 ± 4.9 cm (range: 4.3 - 26 cm) and W of 47.1 ± 66.2 g (range: 1.3 - 383 g), the model of growth of this population (W = 1.2 LT2 - 19.5 LT + 79.36) explains more than 93% of the relationship between W and LT (R2 = 0.9395). Finally, M. olfersii presented an average LT of 6.4 ± 1.3 cm (range: 3.5 - 9.6 cm) and W of 4.2 ± 1.8 g (range: 1.2 – 9.7 g), the growth model of this population (W = 0.22 LT2 - 1.8 LT + 6.5) explains more than 60% of the relationship between W and LT (R2 = 0.621) in females and less than 30% in males (R2 = 0.294).