Reproductive aspects of the flag cichlid Mesonauta insignis in várzea lakes of the Central Brazilian Amazon

Abstract

We describe the most important reproductive aspects of the flag cichlid Mesonauta insignis in the floodplain (várzea) lakes of the Central Brazilian Amazon. Between September 2005 and August 2006, fish were collected monthly from mattresses of aquatic macrophytes. Biometric measurements as well as macroscopic and microscopic analyses of the gonads were performed. Standard body lengths ranged from 2.4 to 9.3 cm, and weight-length relationships were indicative of isometric growth patterns. Reproduction events were detected in all months, but the gonadosomatic index indicated a reproductive season from October to February (during low and rising water periods), reaching a reproductive peak in February. Average fecundity was 1184 ± 40.82 (mean ± SD) mature oocytes. M. insignis exhibits an asynchronous oocytal development, characteristic of multiple spawnings. Morphological and histological analyses indicated 5 gonadal maturation stages for females. Average standard length at first sexual maturation was 5.18 cm for females and 5.5 cm for males. M. insignis shows late sexual maturation. Taken together, these aspects suggest that a life history strategy of ‘equilibrium’ predominates in the species; consequently, M. insignis can be considered vulnerable to high extraction rates, and can only be exploited sustainably if adequate precautionary management procedures are adopted. Some management measures are suggested for the exploitation of this species in the Central Amazon.