Biology subjects

Tilley, A.

Publications and source records attributed to Tilley, A..

3 recordsLinked to original sources

bioRxiv2021

Identifying nearshore nursery habitats for sharks in the Eastern Tropical Pacific from fisheries landings and interviews

The Eastern Tropical Pacific (ETP) comprising the coasts of Costa Rica, Panama, Colombia and Ecuador, represents an area of high marine biodiversity that supports productive fisheries and acts as an important migratory corridor for many marine species. Despite its biological importance, the ETP is understudied and lacks sufficient data for science-based fisheries management and conservation decision-making. This study aims to consolidate understanding of the current and historical distribution of sharks and mobulid rays in the ETP. We used interviews of coastal community stakeholders to document traditional knowledge of shark and mobulid ray species and distributions. We also analysed small-scale fisheries landings data, where available, to quantify local exploitation patterns and the importance of sharks and rays in small-scale fisheries catches. All shark species landed in the dominant nearshore gillnet fishery show very low mean individuals weights (<5 kg), indicating that the fisheries are dominated by juveniles, captured. Aside from smooth-hounds (Mustelus spp.), the scalloped hammerhead shark, Sphyrna lewini, is the most frequently landed shark species in the region by weight and number, with peaks in abundance between April - July. From 132 interviews in 51 communities across the three countries, and landings data from two small-scale fisheries sites, we identified 41 sites in 12 broad geographical zones as important shark nursery habitats. Of these sites, 68% were associated closely with large mangrove systems of the ETP, highlighting the importance of this habitat for shark life history. No patterns were seen in the occurrence or distribution of mobulid rays in coastal areas. Marine protected areas and responsible fishing zones cover 37% of identified nursery habitats in the ETP, 30% in Costa Rica, 48% in Panama and 30% in Colombia. These findings provide an important benchmark of the conservation status of sharks in the ETP and allow for the prioritisation of research and policy-making.

ecology↗

bioRxiv2021

Identifying priority areas for research and conservation of the largetooth sawfish Pristis pristis in Colombia and Panama

Sawfishes are considered one of the most endangered families of fishes in the world. Their diadromous ecology and vulnerability to fishing nets have brought most populations to the brink of collapse. Conservation of the surviving populations is hindered by the paucity of historic and contemporary catch and observational records, and assessments of suitable coastal and riverine habitats. Colombia and Panama are two of 14 countries considered as a high priority for the development of species-specific national legal protection of the critically endangered largetooth sawfish (Pristis pristis). To construct a baseline for the temporal and spatial distribution of the largetooth sawfish in Colombia and Panama, we collected historical records from museum databases and from literature over the past century, analysed available small-scale fisheries landings databases, and conducted interviews with fish workers in 38 locations across both countries. We found 257 records of sawfish occurrences across both countries between 1896 and 2015, with 69% of the records before the year 2000. The declining trend in the frequency of observations was corroborated by fishers, who reported fewer sawfish catches over the last 20 years. Using kernel density estimation of recent encounter locations, we identify potential hotspots that may represent extant populations of sawfish. These locations are broadly characterized by their remoteness and high mangrove forest cover. Given the length and cultural diversity of the Pacific coastlines of Colombia and Panama, and the inaccessibility of many of the communities, our findings provide important guidance to target rapid conservation and fisheries interventions to priority areas. We suggest that the relative success of community-managed fishing areas in the region makes this a valuable platform on which to build local stewardship of marine resources, while raising awareness of the need to safeguard critically endangered largetooth sawfish.

ecology↗

bioRxiv2020

PeskAAS: A near-real-time, open-source monitoring and analytics system for small-scale fisheries

Small-scale fisheries are responsible for landing half of worlds fish catch, yet there are very sparse data on these fishing activities and associated fisheries production in time and space. Fisheries-dependent data underpin scientific guidance of management and conservation of fisheries systems, but it is inherently difficult to generate robust and comprehensive data for small-scale fisheries, particularly given their dispersed and diverse nature. In tackling this challenge, we use open source software components including the Shiny R package to build PeskAAS; an adaptable and scalable digital application that enables the collation, classification, analysis and visualisation of small-scale fisheries catch and effort data. We piloted and refined this system in Timor-Leste; a small island developing nation. The features that make PeskAAS fit-for-purpose are that it is: (i) fully open-source and free to use (ii) component-based, flexible and able to integrate vessel tracking data with catch records; (iii) able to perform spatial and temporal filtering of fishing productivity by fishing method and habitat; (iv) integrated with species-specific length-weight parameters from FishBase; (v) controlled through a click-button dashboard, that was co-designed with fisheries scientists and government managers, that enables easy to read data summaries and interpretation of context-specific fisheries data. With limited training and code adaptation, the PeskAAS workflow has been used as a framework on which to build and adapt systematic, standardised data collection for small-scale fisheries in other contexts. Automated analytics of these data can provide fishers, managers and researchers with insights into a fishers experience of fishing efforts, fisheries status, catch rates, economic efficiency and geographic preferences and limits that can potentially guide management and livelihood investments.

scientific communication and education↗