Biology subjects

Beaulaton, L.

Publications and source records attributed to Beaulaton, L..

3 recordsLinked to original sources

bioRxiv2023

Changes in length-at-first return of a sea trout (Salmo trutta) population in northern France

The resilience of sea trout populations is increasingly concerning, with evidence of major demographic changes in some populations. Based on trapping data and related scale collection, we analysed long-term changes in body length of a sea trout population in the Bresle River, France. From 1984-2022, the length of first-time returning individuals decreased by 1.73 mm.year-1 (SD = 0.08), which resulted in the loss of c. 12.3% of mean body length. This decrease results from a decrease in the age at first return, with a gradual loss of the oldest individuals and an increase in the proportion of the youngest. Timing of the return migration advanced drastically, although shorter sea sojourn had little influence on body length. We found little evidence of a decrease in length-at-age, to the exception of the oldest age class, suggesting that growth conditions at sea might not have deteriorated greatly during the study period.

ecology↗

bioRxiv2022

Modelling the distribution of rare and data-poor diadromous fish at sea for protected area management

Anthropogenic pressures have resulted in declines in diadromous fish. Many diadromous fish which were commercially important are now threatened and protected. Little is known about their marine life history phases, and no observation-based Species Distribution Model exists for this group of species at sea. Yet, fisheries dependent and independent data could provide new insights into the distribution of diadromous fish at sea. We collated a database of 168 904 hauls from fisheries observer bycatch data and scientific fisheries surveys, from eastern Atlantic and Mediterranean waters. The distribution of eleven rare and data-poor diadromous fish (shads, lampreys, salmonids, the European eel, the thinlip mullet, smelt and the European flounder) were modelled. A Bayesian site occupancy model, that incorporates imperfect detection to account for repeat detections and non-detections, the non-random nature of fishing gear type and spatial autocorrelation was used. From the model outputs, we explored bycatch risk and the role of MPAs, required under the Marine Strategy Framework Directive and Habitat Directive and assessed. Diadromous fish were observed within relatively shallow coastal areas. Species specific gear bycatch trends were observed. Core distribution areas corresponded to their known water basin presence, indicating connectivity with their freshwater habitats. Numerous Habitat Directive Marine Protected Areas were found to be of relevance. Given the coastal distribution of these species, they are exposed to higher anthropogenic pressures from both terrestrial and marine environments. Risk of bycatch at sea for most species appears to be low. Nonetheless, for threatened individuals, even a small amount of bycatch may impact their populations, especially since misreporting is likely to be high. Differences in catchability between gears highlight potential benefits of limiting access of certain gears within protected areas to reduce bycatch.

ecology↗

bioRxiv2018

Flow-wise or path-wise: diffusion in a fragmented dendritic network and implications for eels

The European eel (Anguilla anguilla) is a catadromous species that reproduces at sea and inhabits continental waters during its growth phase. River fragmentation due to obstacles is considered one cause of the decline of this species. However, the colonization process of river catchments by eels is still poorly understood. In this article, we compare two scenarios for the diffusion of eels within river catchments: a path-wise scenario, in which movements are totally random, and a flow-wise scenario, in which movements are partially oriented. Based on these two scenarios, we attempted to predict the distribution of eels within dendritic river catchments, explicitly accounting for the presence of obstacles to movement. The model was fitted to a long-time series of electro-fishing data. The results suggest that the path-wise scenario is more predominant than the flow-wise scenario. Moreover, results show that the distribution of eels in river catchment depends on (i) the types of movements carried out by eels, (ii) the configuration of river networks and (iii) the positions of obstacles within catchments.

ecology↗