Drivers of behaviour and spatial ecology of the small spotted catshark (Scyliorhinus canicula)

Abstract

1. Shark populations have suffered dramatic declines across the world as a result of overfishing.2. Marine protected areas (MPAs) can help restore overfished populations; however, their effectiveness largely relies on understanding the ecology of the targeted species.3. This study investigated the spatial ecology of the intensely harvested but understudied small spotted catshark (Scyliorhinus canicula) through acoustic telemetry in the Cíes Islands, a small MPA in the north-west of the Iberian Peninsula.4. There were significant effects of diel, seasonal cycles, biotic (sex and total length) and abiotic (bottom sea temperature) variables on the spatial behaviour of S. canicula. The mean residency index was low (0.27) and movement patterns suggested a strong connection with inshore waters. While the probability of presence in the study area was mainly driven by sex (i.e. greater for females), a drastic increase in activity was observed at night (compared with daytime hours).The activity space decreased with larger body sizes. Warmer waters were related to higher activity levels and larger activity spaces.5. This study provides essential knowledge of the spatial behaviour of S. canicula, with significant implications for the conservation and management of this species.The results indicate that small MPAs may fail to protect the whole range of movements of S. canicula, but suggest a larger protection potential for females. 6. To be effective for S. canicula conservation, MPAs should be appropriately sized and designed for the ranging behaviour of the target species in order to provide total protection. Temporal restrictions on fishing at night mirroring the peak activity pattern of S. canicula could be implemented to limit the probability of its capture.

Drivers of the spatial behaviour of the threatened thornback skate (Raja clavata)

“…The telemetry data revealed the many instances (70) during when R. clavata individuals travelled outside the array to later return. These observations combined with the overall low residency index suggest that R. clavata true home range extends far beyond the limit of the study area and is in agreement with previous studies conducted on two different elasmobranchs species at this site (Leeb et al, 2021;Papadopoulo et al, 2023). A previous mark-recapture study found that most adult R. clavata were recaptured within 37 km of the release site (Chevolot et al, 2006).…”

“…Interestingly, R. clavata demonstrated high consistency in the sector taken to exit and re-enter the array with the majority of excursions heading to the Ría de Vigo. This result mirrors the excursion patterns of S. canicula at the same site (Papadopoulo et al, 2023) and suggests importance of the inshore waters of the Ría de Vigo for coastal elasmobranchs. Notably, although R. clavata appears to follow a specific route for entering and exiting the array, it is important to acknowledge that our approach points to the most probable direction taken after leaving the array, but it does not provide confirmation of the final destination of the excursions.…”

“…Similar to R. clavata, R. undulata displayed a peak in its probability of presence during the summer, while its highest activity space occurred in late spring (Leeb et al, 2021). In contrast, S. canicula had the lowest probability of presence in summer and did not exhibit significant variations in its activity space throughout the year (Papadopoulo et al, 2023). (2) Mirroring S. canicula, R. clavata prefered sector for exiting and reentering the array was the sector pointing towards the Ría de Vigo.…”

“…This alone suggests that small MPAs of just a few square kilometres are probably not enough to protect this species over long periods of time. It is important to point out the pronounced difference in residency between Scyliorhinus canicula RI (0.27) and R. clavata RI (0.073) in the same study area (Papadopoulo et al, 2023). An alternative explanation for the limited use of the study area by R. clavata may indicate a higher level of residence in a nearby area or to sporadic dispersal movements.…”

Presence and Potential Effects of Microplastics in the Digestive Tract of Two Small Species of Shark from the Balearic Islands

“…In the Mediterranean Sea, reports of ingestion and entanglement in sharks with various degrees of endangerment status have been reported [23,29,30]. Two shark species, the small-spotted catshark Scyliorhinus canicula and the blackmouth catshark Galeus melastomus, are not only commercially important species in the Balearic Islands in the western Mediterranean Sea, but the ecological assessment of these species, such as condition index, could be an indication of ecosystem health [31,32]. S. canicula is the most abundant elasmobranch species on the continental shelf [33].…”