Freshwater goby life history in a Mediterranean stream

The Italian goby Gobius nigricans is a running-water-dwelling species inhabiting the Tuscano-Latium district and threatened by several human activities. Many aspects of its biology are currently unknown, such as the dynamic potentialities. Since age determination and dynamic assessment are considered an important tool for a correct management strategy, we aimed to investigate some aspects of the Italian goby life history by applying the fish stock assessment principles, collecting data on fertility, population structure (age-class number), growth (i.e., curvature parameter and asymptotic length), mortality (natural and due to the fishing), and longevity of a central Italian goby population to know the status and dynamic properties of the Italian goby in Mediterranean river systems and to provide a baseline for comparison with other populations. Females are subject to a strong selective pressure to quickly reach a small size to optimize reproductive output, while acquisition of a large size favored males for a more easy access to breeder females (the asymptotic length was higher in males than in females). Moreover, appreciable between-sex differences were found in both growth pattern (the growth rate was lower in females than in males) and dynamic potentialities. In particular, the mortality rate was lower in females, whereas the longevity was slightly lower in males, although the two sexes showed similar values for the two latter properties. There is considerable scope for further work on the G. nigricans growth and other freshwater gobies because information on population and dynamic properties, and assessment of factors affecting growth are still very insufficient.