Romagnoni, Giovanni ORCID: and Dudeck, Tim ORCID: (2024) IMFACT - Integrated Monitoring of Fish Abundance using Combined Tools. , ed. by Leibniz Centre for Tropical Marine Research, ZMT. , Bremen, 40 pp. DOI

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Visual census is a commonly used method for monitoring fish abundance in Marine Protected Areas (MPAs) and coastal seas. Its reliance on human vision and on scuba diving however presents many limitations and biases. The IMFACT project proposes to complement common visual census applications with an integrated toolbox composed of a Remotely Operated Vehicle (ROV) and a hydroacoustic system, to advance monitoring of fish abundance and diversity in coastal areas and MPAs. The integrated approach we propose should ideally complement traditional diving-based visual census, providing a holistic picture (covering areas, species and mechanisms under-surveyed by visual census) and more accurate estimates of fish abundance (accounting for observation bias intrinsic in visual census). The project scoped three objectives: 1) Identify and quantify bias in visual census (e.g. fish escape response triggered by visual census operated by a snorkeler) through ground-truthing using the hydroacoustic array. 2) Explore the feasibility of a) monitoring fish in deeper coastal waters (ca. 30-80 m) with both tools, extending to previously under-monitored areas, while reducing the risk for operators; b) utilizing the hydroacoustic array to monitor pelagic fish in the water column and c) monitoring fish inshore-offshore nightly migrations; 3) develop a protocol for integrated monitoring based on the results.
The project objectives were fully explored and, to a major extent, reached. It was, for example, possible to identify biases caused by the alternative sampling methods: while the quantification of bias was not as straightforward, the project pinpointed alternative approaches suitable for such quantification. The combined toolbox was indeed effective in monitoring fish acoustically and visually at various depths, and in detecting mobile species including small and large demersal and pelagic fish, which are key resources for small-scale fisheries and for tourism.
While caveats and limits have been identified, it emerges clearly that the proposed approach may be highly suitable for monitoring fish abundance, biomass and behaviour in coastal demersal and pelagic areas. Our toolbox could thus enable MPA managers and scientists to improve accuracy in the estimation of fish abundance and biodiversity, ultimately facilitating sustainable fisheries management and contributing to MPAs conservation goals.
The project relied on close interaction with local partners and stakeholders in the selected study area, the Caribbean island of Bonaire (The Netherlands). Through a close collaboration with STINAPA, the agency in charge of the MPA management and enforcement in Bonaire MPA, key aspects of interest for multiple stakeholders were identified. These included monitoring of habitats and species of conservation and commercial interest, conflict resolution, effectiveness of spatial closures for various user groups including small scale fishers, tourism operators, and environmental NGOs. The project also confirmed the suitability of Bonaire as an interesting research area suitable for testing tools and approaches and highly interesting for further studies in this field.

Document Type: Report (Project Report)
Programme Area: PA1
Research affiliation: Ecology > Fisheries Biology
Integrated Modelling > Spatial Ecology and Interactions
Projects: IMFACT
Date Deposited: 12 Jun 2024 14:36
Last Modified: 12 Jun 2024 14:36

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