Fecundity, egg and alevin size in the River Irminio population of the threatened Salmo cettii Rafinesque-Schmaltz, 1810 (Sicily, Italy)

Abstract

Summary This study reports the first available data on the reproductive biology of an Italian Salmo cettii trout population. Fecundity, egg and larvae size were determined in 38 females collected by electro‐fishing before spawning (January–February, 1993 and 1994) in the River Irminio (SE Sicily, Italy; 36°57′36″N; 14°46′18″E), probably the southernmost trout river in Europe. The smallest ripe female was 16.3 cm long and the largest 31 cm (SL). Fecundity was described according to: Log F = −0.669 + 2.592 × Log SL, which is comparable to the most fecund European trout populations. This can be explained by the productivity of this river: on the basis of the results it was not possible to use fecundity to discriminate between nominal brown trout and Mediterranean trout (i.e. no taxonomic fecundity differences were found) nor to show clear‐cut differences in fecundity between Atlantic and Mediterranean habitats. Bigger females produced significantly larger eggs, which in turn produced significantly longer alevins at hatch. This significantly positive relationship was still present after 15 days and at the resorption of the yolk sac. The interplay between high fecundity and large egg diameter (i.e. high allocation in egg mass) could be particular to this trout, and produced very high GSI values that showed no significant relationship to length. The data reported in this study are particularly important for the design and implementation of effective management and conservation measures for this threatened trout species.

Native Population Structure beyond Hatchery Introgression in the Endemic Sicilian Trout

“…In Irminio, there are no previous genetic data on introgression in this basin, apart from one analyzed specimen from the main river that was a hybrid for the LDH-C* locus [7]. Our extensive sampling in this basin found an important level of hatchery introgression in both the Irminio Main River and all its tributaries (q = 0.167-0.409), which agrees with the intensive stocking practices reported [19].…”

“…Apart from water abstraction, poaching, overfishing or pollution, one of the main threats to Sicilian populations is stocking with non-native brown trout [5,6,14]. As has occurred in other Mediterranean regions, stocking with hatchery-reared brown trout of Northern European origin has been a common practice to counteract the effects of overfishing in Sicilian rivers [8,18,19], which has inevitably lead to genetic consequences [7,8]. In the Ragusa province, the most studied area, stocking with hatchery brown trout of Northern European origin stopped at the end of the 1980s, when the artificial breeding of local trout was started at a local hatchery [19,20].…”

“…As has occurred in other Mediterranean regions, stocking with hatchery-reared brown trout of Northern European origin has been a common practice to counteract the effects of overfishing in Sicilian rivers [8,18,19], which has inevitably lead to genetic consequences [7,8]. In the Ragusa province, the most studied area, stocking with hatchery brown trout of Northern European origin stopped at the end of the 1980s, when the artificial breeding of local trout was started at a local hatchery [19,20]. Bobbio et al [21] were the first to describe the genetic distinction between Sicilian and other trout of Atlantic origin.…”

Flank spot number and its significance for systematics, taxonomy and conservation of the near‐threatened Mediterranean troutSalmo cettii: evidence from a genetically pure population

“…This could explain the difference between the values found in Tellesimo and those counted by Sommani () in the introgressed population of the Anapo River. In addition, some preliminary observations in the Irminio River, where alien hatchery S. trutta have been stocked (Duchi, ), have found spot numbers between four and 48 (A. Duchi, unpubl. data), i.e .…”

Spawning and habitat management in salmonid populations at the southern edge of their natural ranges = Reproducción y gestión del hábitat en poblaciones de salmónidos en el extremo meridional de sus distribuciones naturales

“…In addition, Caputo et al (2010) also detected some small females spawning in February and March in the river Metauro. Moreover, Gibertini et al (1990) reported that a native trout population (tentatively Salmo cettii) from the Posta Fibreno lake (Central Apennines, Italy) reproduces from January to March and Duchi (2011) reported that a native Salmo cettii trout population from southeastern Sicily spawns during January and February.…”