Scheda di dettaglio – i prodotti della ricerca
| Dato | Valore |
|---|---|
| Title | 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 |
| Abstract | Salmonid species are main actors in the Italian socio-ecological landscape of inland fisheries. We present novel data on the size-age structure of one of the remnant Italian populations of the critically endangered marble trout Salmo marmoratus, which co-occurs with other stocked non-native salmonids in a large glacial river of the Lake Maggiore basin (Northern Italy-Southern Switzerland). Like other Italian native trout populations, the Toce River marble trout population is affected by anthropogenic introgression with the non-native brown trout S. trutta. Our sample includes 579 individuals, mainly collected in the Toce River main channel. We estimated the length-weight relationship, described the population size-age structure, estimated the age-specific growth trajectories, and fit an exponential mortality model. A subset of the sample was also used to measure numerical and biomass density. The estimated asymptotic maximum length is ~105 cm total length (TL). Mean length at first maturity is ~55 cm TL, and mean length at maximum yield per recruit is ~68 cm TL. Approximately 45-70% of the population are estimated to die annually, along with a fishing annual mortality of ~37%, with an exploitation ratio of ~0.5. The frequency distribution of length classes in a sample collected by angling shows that ~80% of the individuals that could be retained according to the current recreational fishing regulations likely never reproduced, and large fish disproportionally contributing to recruitment are fished and retained. We identify possible overfishing risks posed by present regulations, and propose updated harvest-slot length limits to mitigate such risks. More detailed and long-term datasets on this system are needed to more specifically inform the fishery management and monitor the effects of any change in the management strategy on the size-age structure of the marble trout population of the Toce River. |
| Source | PeerJ 11:e14991 |
| Keywords | SalmonidsFish body growthFish population structureFishing mortalityFish conservationAlpine riversLIFE programToce River |
| Journal | PeerJ |
| Editor | , , |
| Year | 2023 |
| Type | Articolo in rivista |
| DOI | 10.7717/peerj.14991 |
| Authors | Gianluca Polgar, Mattia Iaia, Paolo Sala, Tsung Fei Khang, Silvia Galafassi, Silvia Zaupa, Pietro Volta |
| Text | 481701 2023 10.7717/peerj.14991 Salmonids Fish body growth Fish population structure Fishing mortality Fish conservation Alpine rivers LIFE program Toce River 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 Gianluca Polgar, Mattia Iaia, Paolo Sala, Tsung Fei Khang, Silvia Galafassi, Silvia Zaupa, Pietro Volta Water Research Institute IRSA CNR, Verbania Pallanza, VB, Italy Institute of Mathematical Sciences, Faculty of Science, Universiti Malaya, Kuala Lumpur, Malaysia Universiti Malaya Centre for Data Analytics, Universiti Malaya, Kuala Lumpur, Malaysia Salmonid species are main actors in the Italian socio ecological landscape of inland fisheries. We present novel data on the size age structure of one of the remnant Italian populations of the critically endangered marble trout Salmo marmoratus, which co occurs with other stocked non native salmonids in a large glacial river of the Lake Maggiore basin Northern Italy Southern Switzerland . Like other Italian native trout populations, the Toce River marble trout population is affected by anthropogenic introgression with the non native brown trout S. trutta. Our sample includes 579 individuals, mainly collected in the Toce River main channel. We estimated the length weight relationship, described the population size age structure, estimated the age specific growth trajectories, and fit an exponential mortality model. A subset of the sample was also used to measure numerical and biomass density. The estimated asymptotic maximum length is 105 cm total length TL . Mean length at first maturity is 55 cm TL, and mean length at maximum yield per recruit is 68 cm TL. Approximately 45 70% of the population are estimated to die annually, along with a fishing annual mortality of 37%, with an exploitation ratio of 0.5. The frequency distribution of length classes in a sample collected by angling shows that 80% of the individuals that could be retained according to the current recreational fishing regulations likely never reproduced, and large fish disproportionally contributing to recruitment are fished and retained. We identify possible overfishing risks posed by present regulations, and propose updated harvest slot length limits to mitigate such risks. More detailed and long term datasets on this system are needed to more specifically inform the fishery management and monitor the effects of any change in the management strategy on the size age structure of the marble trout population of the Toce River. 11 e14991 Published version Articolo in rivista 2167 8359 PeerJ PeerJ ZAUPA SILVIA mattiaiaia IAIA MATTIA POLGAR GIANLUCA pietro.volta VOLTA PIETRO silvia.galafassi GALAFASSI SILVIA |