Laura Pompei

Proposed Empirical Standard Weight Equation for Brook Chub Squalius lucumonis

Abstract Relative weight (Wr ) is an index of condition that enables evaluation of the well-being of fish by comparing the actual weight of a specimen with the ideal weight of a specimen of the same species and the same length that is in good physiological condition (i.e., the standard weight [Ws ]). This index was primarily developed to assess the status of sport fishes. Recently, however, many authors have encouraged the use of this index as a fisheries assessment tool for nongame species as well, especially those that are endangered or threatened. Length and weight data on brook chub Squalius lucumonis, an Italian endemic species listed as endangered by the International Union for the Conservation of Nature, were collected across its area of distribution and used to compute a standard weight (Ws ) equation by means of the empirical percentile method. The Ws equation thus obtained (log10 Ws = –7.75 + 5.75 log10[total length {TL}] – 0.66 [log10TL]2; TL range of application = 90–210 mm) was not biased by ...

Reproductive parameters in native and non-native areas of Padogobius bonelli and comparison with P. nigricans (Actynopterigii, Gobiidae)

The introduced goby Padogobius bonelli has established abundant populations in the River Tiber basin (Central Italy) and its expansion coincided with the decrease of the endemic P. nigricans. P. bonelli exhibits a more aggressive behaviour than P. nigricans, but other biological attributes may advance its colonization success. To test this hypothesis, some reproductive parameters (gonado-somatic index, age at maturity, egg size, absolute and relative fecundity) of a long-time established non-native population of P. bonelli were analysed and compared to a population from the native area as well as to those of P. nigricans inhabiting the same river. As a result, no differences between non-native and native populations of P. bonelli were observed. On the contrary, non-native P. bonelli showed higher values of gonado-somatic index for both sexes, a more protracted spawning season and produced a greater number of eggs than P. nigricans. These results indicated a greater reproductive output of P. bonelli that can enhance its invasion process and favour the expansion outside of its native range, causing further decline of P. nigricans populations.