The Italian Alpine and Subalpine trouts: Taxonomy, Evolution, and Conservation

Abstract

During the last 150 years, the trout-culture industry focused on enhancing trout populations by stocking, in response to the growing anglers’ demand and the habitat degradation associated to the rapid urbanization and hydropower development. The industrialized north of Italy, home to the Italian Alpine and subalpine trout populations, is the source of most of the revenues of the national trout-culture industry. Its rapid growth, and the massive introduction of non-native interfertile trouts eroded the genetic diversity of native lineages, leading to harsh confrontations between scientists, institutions, and sportfishing associations. We review here the state of the art of the taxonomy and distribution of the northern Italian native trouts, presenting both scientific results and historical documentation. We think the only native trouts in this region are Salmo marmoratus, widespread in this region, plus small and fragmented populations of S. ghigii, present only in the South-western Alps. We strongly recommend the interruption of stocking of domesticated interfertile non-native trouts in this area, and recommend the adoption of Evolutionary Significant Units for salmonid fishery management. We further propose future research directions for a sustainable approach to the conservation and ecosystem management of the fishery resources and inland waters of northern Italy.

What’s the effectiveness of stocking actions in small creeks? The role of water discharge behind hatchery trout downstream movement

“…Millions of hatchery-reared trout are still released into creeks/streams every year ( Waples, 1999 ; Aprahamian et al, 2003 ; Brockmark & Johnsson, 2010 ; Polgar et al, 2022 ) despite their fate and survival being largely unknown after the release into the wild. Furthermore, a few studies have investigated the environmental variables behind the movements of hatchery-reared brown trout following their release into water courses, especially in creeks and little streams ( Helfrich & Kendall, 1982 ; Pedersen, Dieperink & Geertz-Hansen, 2003 ; Aarestrup et al, 2005 ).…”

The Use of Ovarian Fluid as Natural Fertilization Medium for Cryopreserved Semen in Mediterranean Brown Trout: The Effects on Sperm Swimming Performance

“…17). Recent studies suggest that Italian peninsular Mediterranean brown trout belong to a separate taxon named S. ghigii, limiting the name S. cettii to Sicilian trout [ 48 , 49 , 50 ]. Although we agree with the recent observations, we still use the name S. cettii in the current paper, because Mediterranean brown trout populations are still protected by the Habitat Directive and subsequent updates on its conservation status.…”

Size-age population structure of an endangered and anthropogenically introgressed northern Adriatic population of marble trout (Salmo marmoratus Cuv.): insights for its conservation and sustainable exploitation

“…Three types of stocking management ( Lorenzen, Beveridge & Mangel, 2012 ) are practiced in VCO: culture-based fisheries of non-native species (production-oriented), including (i) a put-grow-and-take fishery of S. trutta and of Salmo ghigii Pomini, 1941 ( sensu Polgar et al, 2022 ), variably introgressed with S. trutta ( Splendiani et al, 2019 ) and commercially referred to as ‘Mediterranean brown trout’ (mainly Lake Maggiore, upper Toce River and most tributaries); (ii) a put-and-take fishery of Oncorhynchus mykiss Walbaum, 1792 (upper Toce River and some of its tributaries); and (iii) a stock-enhancement fishery (supportive breeding) of S. marmoratus (mainly Lake Maggiore and Lake Orta, middle and lower tracts of the Toce River, and several tributaries).…”

“…Manipulation was reduced to a minimum, and the fish was immediately released after measurements. Sampled individuals were Salmo specimens with marbled elements (spots with amoeboid shape) in their coloration pattern, thus including ‘genetically pure’ S. marmoratus , S. trutta × S. marmoratus hybrids, and variably introgressed individuals ( Delling, 2002 ; Djurdjevič et al, 2019 ; Lorenzoni et al, 2019a , 2019b ; Polgar et al, 2022 ; Fig. S1 ).…”

“…Among salmonids, marbled coloration traits are also present in (i) hybrids between S. marmoratus and domesticated stocks of North-European brown trout ( Delling et al, 2000 ; Djurdjevič et al, 2019 ; S. trutta Linnaeus, 1758 sensu Segherloo et al, 2021 ), (ii) at least one population of S. trutta (Otra River, Norway; Delling, 2002 ), and (iii) hybrids between salmonid species of different genera ( Miyazawa, Okamoto & Kondo, 2010 ). S. marmoratus includes two geographically distinct populations, in the Northern and Southern Adriatic regions ( Delling et al, 2000 ; Polgar et al, 2022 and references therein). In the North Adriatic region, this species is distributed in the middle and lower tracts of the orographic left tributaries of the Po River, a few of the small orographic right tributaries of the Po River in the Southwestern Alps, and several large rivers flowing into the Adriatic Sea ( Fig.…”