Abstract
North American black bullhead, Ameiurus melas, which were introduced to Europe in the nineteenth and twentieth centuries, have received relatively little study. With focus on growth and reproduction, this extensive review, which includes new European data, aims to inform the risk analysis process concerning this non-native species in Europe. Surprisingly, the new data for Europe were more comprehensive than for native populations, with data available mainly from Oklahoma, and North and South Dakota (USA). In terms of relative growth, juvenile A. melas were found to have a relatively uniform body shape regardless of the population’s origin, whereas adults developed different phenotypes depending upon location. Overall growth trajectory was significantly faster for native than for non-native populations. Growth index values decreased significantly with increasing latitude in non-native but not native populations—the latter decreasing weakly with increasing altitude in the populations located at latitudes <40°. Mean general condition (slope ‘b’), mean sex ratio and mean egg diameter did not differ significantly between native and non-native populations. Absolute fecundity was slightly (but not significantly) higher in non-native than native populations. GSI data, which were very scarce for native populations, suggest gonad production may be slightly higher in native than in non-native populations. Precise data on age at maturity (AaM) are lacking for the native range, where 2–5 years is reported. Whereas, in the introduced range the greatest AaM was 3.5 years, and AaM decreases with increasing juvenile growth (TL at age 3). The populations with fastest juvenile growth tended to be from warmer water bodies where they are considered to be invasive. The great growth and life-history plasticity of black bullhead affords the species great potential to invade and establish viable populations in new areas.
Highlights
The introduction to Europe of non-native freshwater fishes from North America has a long history (Copp et al 2005a), beginning with salmonid and centrarchid and ictalurid species
Body lengths were mostly given as total length (TL), but in cases where standard length (SL) was given, SL was converted to TL using the mean conversion factor (1.199) calculated from 12 conversion factors reported in Carlander (1969)
When geographical coordinates of the study area were not indicated in a bibliographic source, the coordinates were derived from on-line search engines and map coordinate conversion tools, with representative mean coordinates used when samples were collected over a large area and approximate coordinates when precise locations were not reported and could not be obtained from local sources
Summary
The introduction to Europe of non-native freshwater fishes from North America has a long history (Copp et al 2005a), beginning with salmonid and centrarchid and ictalurid species. Fobert et al 2013); and (3) human-assisted dispersal such as unauthorized fish movements and releases for angling amenity or religious reasons (Copp et al 2005b) Concurrent with this recent work on pumpkinseed, studies of black bullhead life-history traits have become very topical due to the species’ recent arrival and/or expansion in Continental and southern European inland waters In view of the limited data on the species, available data on both females and males are included here where possible; this contrasts current work on pumpkinseed, which has mainly been restricted to females because male reproductive indices are poor indicators of population responses to environmental variability (see Danylchuk and Fox 1994)
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