ABSTRACT
During the second phase (c.1925-1960s), introductions continued within countries with established populations, and also commenced in increasingly marginal and/or less populous regions. For instance, Venezuela and Papua New Guinea, two equatorial countries with potentially suitable highland areas, received multiple shipments of brown trout in the 1940s and 1950s (MacCrimmon et al, 1970). Similarly, brown trout were liberated in subtropical portions of the US (e.g. Hawaii) between 1930 and 1960. Not surprisingly, the establishment of naturally reproducing populations was less successful during this period, and the prevalence of ‘put-and-take’ fisheries (i.e. populations maintained only through release of cultured trout) increased markedly (Crawford and Muir, 2008). By the end of the 1960s, MacCrimmon and Marshall (1968, p2542) regarded ‘the dissemination of European brown trout … to have been so complete … that most areas of the world capable of supporting significant natural populations have now received introductions’. The last phase of range expansion (1960s to present) is one characterized by the maintenance of some local populations through stocking programmes and a general cessation of broadscale introduction efforts.
