Most Elasmobranch species globally are classified as "critically endangered" by the IUCN mainly due to overfishing and in the Mediterranean Sea, always considered a biodiversity hotspot, this decline is particularly accentuated. Although commercial fishing is the main cause of this phenomenon, recreational fishing represents a growing threat but data available to quantify its impact remain scarce. This thesis project aims to fill this gap by studying the interaction between recreational fishing and elasmobranchs in the waters of the Northern Adriatic, with the main objective of quantifying the elasmobranch species caught and their spatial-temporal distribution. Data were obtained through questionnaires given to recreational fishermen during their fishing sessions and through logbooks filled in by the most collaborative fishermen. The analysis focused on different types of sport fishing: drifting, spinning… The data collected during the fishing season (April-October) are processed using QGIS software to analyze the spatial component and using statistical methods to evaluate the trend of fishing effort and catch per unit effort (PUE) in the period April-October 2024. The results show greater interactions between drifting fishing and elasmobranchs attributable to the species Prionace glauca (79%), Alopias vulpinus (18%), Carcharhinus plumbeus (3%) which present peaks of observations in the months of May, June and July; the spatial analysis of their catches highlights a concentration in the areas surrounding the Po river mouth where the largest catches of both P. glauca and A. vulpinus were also recorded. The analysis of catches made with fishing methods other than drifting shows a predominance of Mustelus spp., mainly fished near the inlets and dams, but also the presence of Pteroplatytrygon violacea with a massive concentration at the mouth of the Brenta and myliobatids detected near the Chioggia and Malamocco Dams with an isolated catch off Pila. This pilot study provides useful information for the sustainable management of elasmobranchs in the Northern Adriatic, highlighting how the impact of recreational fishing is also relevant on these species and that there is a need for further research to develop effective conservation strategies. The multidisciplinary approach, which combines field data collection with those deriving from the experience of fishermen, represents a model for future studies on the interaction between human activities and elasmobranch populations in the Northern Adriatic Sea.
La maggior parte delle specie di elasmobranchi a livello globale sono classificate come "in pericolo critico" dalla IUCN principalmente a causa della pesca eccessiva e nel Mar Mediterraneo, considerato da sempre un hotspot di biodiversità, questo declino è particolarmente accentuato. Sebbene la pesca commerciale sia la causa principale di questo fenomeno, la pesca ricreativa rappresenta una minaccia crescente ma i dati disponibili per quantificarne l'impatto rimangono scarsi. Questo progetto di tesi si propone di colmare questa lacuna studiando l'interazione tra pesca ricreativa ed elasmobranchi nelle acque dell'Alto Adriatico, con l'obiettivo principale di quantificare le specie di elasmobranchi catturate e la loro distribuzione spazio-temporale. I dati sono stati ottenuti attraverso questionari posti ai pescatori ricreativi durante le loro sessioni di pesca e tramite logbooks compilati dai pescatori più collaborativi. L’analisi si è focalizzata su diverse tipologie di pesca sportiva: drifting, spinning… I dati raccolti durante la stagione di pesca (aprile-ottobre) vengono elaborati tramite software QGIS per analizzare la componente spaziale e tramite metodi statistici per valutare l'andamento dello sforzo di pesca e delle catture per unità di sforzo (PUE) nel periodo aprile-ottobre 2024. I risultati indicano maggiori interazioni tra pesca a drifiting ed elasmobranchi riconducibili alle specie Prionace glauca (79%), Alopias vulpinus (18%), Carcharhinus plumbeus (3%) che presentano picchi di osservazioni nei mesi di maggio, giugno e luglio; l'analisi spaziale delle loro catture evidenzia una concentrazione nelle zone limitrofe alle foci del Po dove si sono anche registrate le maggiori catture sia di P. glauca che di A. vulpinus. L’analisi delle catture effettuate con tipologie di pesca differenti dal drifting mostra una predominanza di Mustelus spp., pescato principalmente in prossimità delle bocche di porto e delle dighe, ma anche la presenza di Pteroplatytrygon violacea con una massiccia concentrazione alle foci del Brenta e miliobatidi rilevati in prossimità della Diga di Chioggia e Malamocco con una cattura isolata al largo di Pila. Questo studio pilota fornisce informazioni utili per la gestione sostenibile degli elasmobranchi nell'Alto Adriatico evidenziando come anche l'impatto della pesca ricreativa sia rilevante su queste specie e ci sia la necessità di ulteriori ricerche per sviluppare strategie di conservazione efficaci. L'approccio multidisciplinare, che combina la raccolta di dati sul campo con quelli derivanti dall’esperienza dei pescatori, rappresenta un modello per futuri studi sull'interazione tra attività antropiche e le popolazioni degli elasmobranchi nel Mar Adriatico settentrionale.
Analisi dell’interazione tra pesca ricreativa ed elasmobranchi nel Nord Adriatico.
PAVAN DALLA TORRE, DIEGO
2024/2025
Abstract
Most Elasmobranch species globally are classified as "critically endangered" by the IUCN mainly due to overfishing and in the Mediterranean Sea, always considered a biodiversity hotspot, this decline is particularly accentuated. Although commercial fishing is the main cause of this phenomenon, recreational fishing represents a growing threat but data available to quantify its impact remain scarce. This thesis project aims to fill this gap by studying the interaction between recreational fishing and elasmobranchs in the waters of the Northern Adriatic, with the main objective of quantifying the elasmobranch species caught and their spatial-temporal distribution. Data were obtained through questionnaires given to recreational fishermen during their fishing sessions and through logbooks filled in by the most collaborative fishermen. The analysis focused on different types of sport fishing: drifting, spinning… The data collected during the fishing season (April-October) are processed using QGIS software to analyze the spatial component and using statistical methods to evaluate the trend of fishing effort and catch per unit effort (PUE) in the period April-October 2024. The results show greater interactions between drifting fishing and elasmobranchs attributable to the species Prionace glauca (79%), Alopias vulpinus (18%), Carcharhinus plumbeus (3%) which present peaks of observations in the months of May, June and July; the spatial analysis of their catches highlights a concentration in the areas surrounding the Po river mouth where the largest catches of both P. glauca and A. vulpinus were also recorded. The analysis of catches made with fishing methods other than drifting shows a predominance of Mustelus spp., mainly fished near the inlets and dams, but also the presence of Pteroplatytrygon violacea with a massive concentration at the mouth of the Brenta and myliobatids detected near the Chioggia and Malamocco Dams with an isolated catch off Pila. This pilot study provides useful information for the sustainable management of elasmobranchs in the Northern Adriatic, highlighting how the impact of recreational fishing is also relevant on these species and that there is a need for further research to develop effective conservation strategies. The multidisciplinary approach, which combines field data collection with those deriving from the experience of fishermen, represents a model for future studies on the interaction between human activities and elasmobranch populations in the Northern Adriatic Sea.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/84216