Non‐native fishes are often blamed for exerting adverse ecological impacts on native fishes, but the evidence is circumstantial and the true impacts remain largely unknown. This dilemma is particularly acute for freshwater ecosystems of the Mediterranean Region, where a high level of endemism (a biodiversity hotspot) makes native fish extinctions much more likely because of their small natural ranges. The aim of this paper is to review non‐native fish impacts, from genes to ecosystem level, in the fresh waters of the Mediterranean Region and identify gaps in knowledge that currently hamper effective conservation and management of native species and ecosystems. Most studies reviewed reported potential impacts rather than realised impact mechanisms, and these were conducted predominantly in the European part of the Mediterranean Region. No studies of realised impacts were found for three of the 15 most introduced fishes, which emphasises the need for evidence‐based studies of non‐native species impacts.

Risk assessments are crucial for identifying and mitigating impacts from biological invasions. The Fish Invasiveness Scoring Kit (FISK) is a risk identification (screening) tool for freshwater fishes consisting of two subject areas: biogeography/history and biology/ecology. According to the outcomes, species can be classified under particular risk categories. The aim of this study was to apply FISK to the Iberian Peninsula, a Mediterranean climate region highly important for freshwater fish conservation due to a high level of endemism. In total, 89 fish species were assessed by three independent assessors. Results from receiver operating characteristic analysis showed that FISK can discriminate reliably between noninvasive and invasive fishes for Iberia, with a threshold of 20.25, similar to those obtained in several regions around the world. Based on mean scores, no species was categorized as "low risk," 50 species as "medium risk," 17 as "moderately high risk," 11 as "high risk," and 11 as "very high risk." The highest scoring species was goldfish Carassius auratus. Mean certainty in response was above the category "mostly certain," ranging from tinfoil barb Barbonymus schwanenfeldii with the lowest certainty to eastern mosquitofish Gambusia holbrooki with the highest level. Pair-wise comparison showed significant differences between one assessor and the other two on mean certainty, with these two assessors showing a high coincidence rate for the species categorization. Overall, the results suggest that FISK is a useful and viable tool for assessing risks posed by non-native fish in the Iberian Peninsula and contributes to a "watch list" in this region.

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The present study describes the annual condition as well the length-weight (LWR) and length-length relationships (LLR) of the Asian striped catfish, Mystus vittatus (Bloch, 1794) (Siluriformes: Bagridae), an important fishery in the Mathabhanga River (SW Bangladesh). A total of 2438 specimens (3.60-9.60 cm standard length) used in this study was caught with traditional fishing gear from January to December 2004. Overall, the allometric coefficient b of the LWR was close to the isometric value (b ¼ 3.058), although it suggested negative allometric growth for males (b ¼ 2.959) whilst positive allometric growth for females (b ¼ 3.134). The results further indicated that the LLRs were highly correlated (r 2 > 0.989, P < 0.001). The monthly gonadosomatic index showed that the reproductive period of M. vittatus began in April, and ended in August when the highest values of the Fulton's condition factor (K) indicated their recovery. These results will be useful for fishery managers to impose adequate regulations for sustainable fishery management not only in the Mathabhanga River of Bangladesh but also in neighbouring countries.

The present study describes the length-weight (LWR) and length-length (LLR) relationships for eight important small indigenous fish species (SIS) from the Mathabhanga River, southwestern Bangladesh, namely Amblypharyngodon mola