Tagging effects on three non-native fish species in England (Lepomis gibbosus, Pseudorasbora parva, Sander lucioperca) and of native Salmo trutta

Abstract –  To address the dearth of information on tagging effects and long-term survivorship of tagged fish in native and introduced species, laboratory and field investigations were undertaken on three non-native fish species (pumpkinseed Lepomis gibbosus ; topmouth gudgeon Pseudorasbora parva ; pikeperch Sander lucioperca ) tagged with coded-wire (CW), passive integrated transponder (PIT), radio (RT) telemetry and/or acoustic tags (AT), with survivorship of native brown trout ( Salmo trutta ) examined in the field. Laboratory results revealed high survivorship following tag attachment/insertion and resumption of feeding within 24–48 h of tagging (all mortalities could be attributed to an unrelated outbreak of fungal infection), with retention rates being high in both pumpkinseed and pikeperch but low in topmouth gudgeon (excluded from field studies). In the field, short-term post-operation survival was high in pikeperch, pumpkinseed and brown trout. In pumpkinseed and trout, 100% of RT fish survived a 24–30 day tracking study, with 60% and 80%, respectively, recaptured alive at least 3 months post-tagging. Of PIT tagged pumpkinseed, 44% were recaptured (after 6–18 months), with small-sized, CW-tagged fish (0.38 g weight) captured up to 1 year after tagging. In pikeperch, all AT fish except one (the smallest specimen) survived their full expected tracking period (i.e. tag life) – the single lost specimen survived at least half of its expected tracking period (i.e. 6 month battery life). Overall, the tagging methods used were highly effective in pumpkinseed and pikeperch, showing good retention and survival, but PIT tagging of topmouth gudgeon was plagued by low survivorship and tag rejection.     

Genetic relationships among pumpkinseed (Lepomis gibbosus) ecomorphs in freshwater reservoirs of Portugal

Abstract – High levels of morphological differentiation have been found among pumpkinseeds (Lepomis gibbosus) occupying four habitat types in Portuguese reservoirs. To investigate the underlying mechanism behind the phenotypic differentiation among ecomorphs, we used six microsatellite markers to assess patterns of genetic differentiation among and within eight naturalised reservoir populations. Greater genetic differentiation was seen among reservoir populations than within reservoirs (F_ST > 0.041, P < 0.002). structure analysis revealed the presence of two distinct genetic groups among the set of eight reservoir populations. However, an analysis of co‐occurring forms that were identified a priori by their respective habitats was consistent with a single panmictic group, suggesting that morphological differentiation has arisen in sympatry (i.e., within a reservoir, postintroduction). The observed relationships within and among reservoir populations, combined with the timeframe of ecomorph divergence, suggest the strong likelihood of phenotypic plasticity as the underlying mechanism of diversification in the introduced pumpkinseed.     

Habitat use,home range,movements and interactions of introduced Lepomis gibbosus and native Salmo trutta in a small stream of Southern England

Radio telemetry data were analysed to assess the microhabitat use, movement patterns, home range overlap and interspecific interactions of non‐native pumpkinseed Lepomis gibbosus (L.) and native brown trout Salmo trutta (L.) in a small English stream located immediately below a commercial angling lake from which pumpkinseed escaped. Although both species favoured pool habitats, brown trout preferred higher velocities and coarser substrata compared with pumpkinseed. Also, some individual brown trout preferred deeper waters than did pumpkinseed. Home range area of brown trout was substantially larger than that of pumpkinseed in spring and summer, and for both species, home range area in autumn was significantly smaller than in the other seasons. Range centre distribution analysis revealed that both species were distributed significantly nonrandomly within the stream during all seasons. There was substantial home range overlap between the two species in all seasons, the greatest being in spring. Overall distances moved were greatest during spring for both species, with brown trout moving greater distances relative to pumpkinseed. However, the absence of mutual attraction or avoidance between the species, as well as the lack of cohesion in preferred habitats and strong territorial fidelity, suggests little or no impact of introduced pumpkinseed on resident brown trout.