What’s the catch? More efficient enforcement of fisheries to protect estuarine biodiversity

Three main findings:

  • Spatial priorities for enforcement were similar under different climate events, but varied substantially among seasons;
  • Cost and area enforced varied within scenarios tested – with a modest increase in budget you can account for climate variability;
  • Spatial priorities for enforcement change depending on who is responsible for enforcement.

Coastal lagoons and estuaries are some of the most productive ecosystems in the world.

They act as feeding and breeding grounds and are of economic importance for humans. Because of this, human populations often live close by which leads to habitat loss and problems caused by overfishing.

Small-scale fishing operations that mostly use low-technology angling techniques, known as Artisanal fisheries, support the livelihoods of millions of people around the world. These operations have low running costs, small boats, few fishers per boat, and limited profit.

In Brazil more than 50 per cent of fishery production comes from artisanal fisheries.

However, data for how these smaller operations effect ecosystems is limited, and ineffective enforcement of these endeavours can allow for continued environmental degradation from overexploitation of local fish stocks.

To combat this, we used spatial planning to design an enforcement strategy that considers multiple factors including climate variability, existing seasonal fishing closures, conservation targets, and enforcement costs. Since these priorities vary season to season, a dynamic enforcement strategy offers the best solution.

Figure 1: Spatial priorities for enforcement of artisanal fisheries in the Patos Lagoon estuary when ignoring El Niño Southern Oscillation (ENSO) intensities (Group 1) and when incorporating spatial distribution of species during distinct ENSO intensities as conservation features (Group 3). Selection frequency is how often a planning unit is selected across 100 runs under each scenario. Here, the cost layer used was the estimated enforcement cost by the government.

This is one of the first studies to consider how environmental variability within spatial planning can be used to efficiently optimise enforcement to meet multiple conservation actions.

Most fisheries management in Brazil has focused on control of catch, fish size restrictions, and restricted seasonal areas, enforced by patrols that detect and prosecute illegal activities. With limited enforcement resources, there is an opportunity to use modelling to increase the chance enforcement reduces poaching at a minimum cost.

Combining fisheries data with conservation planning and considering seasonal change, we applied spatial planning tool Marxan, while shifting enforcement from governments to local communities, to design an optimum strategy over space and time for Patos Lagoon estuary in Brazil. We aimed to protect 25% of each of our main species considered in the seasonal fishing closure and 10% of the remaining estuarine biodiversity for each scenario tested.

Figure 2: Mean cost and area selected to enforce the artisanal fishery in the Patos Lagoon estuary. Results displayed in this graph represent scenarios from Group 1, 2 and 3: A) El Niño and B) La Niña, C) enforcement by environmental agency and D) enforcement by fishers.
Our approach is extremely flexible and can be modified to address different enforcement needs.
Figure 4: Co-participative enforcement plan proposed to protect estuarine resources and biodiversity at the Patos Lagoon estuary. This plan is based on the selection frequency results (≥ 80%) from scenarios including climate variability as conservation features (Group 3): A) winter, B) spring, C) summer, and D) autumn).

Our findings demonstrate that enforcement costs can be potentially reduced when community members are involved in the enforcement process.

This is extremely important in countries like Brazil, where low budget and lack of resource are a constant reality. In this case, we do recommend that a temporally dynamic enforcement included in a community-based management can bring substantial savings on costs to increase the sustainability of estuarine resources.

Media: Dr Micheli Duarte de Paula Costa, duarte.micheli@yahoo.com.br; Casey Fung, c.fung@uq.edu.au, +614 433 638 643.

Dr Micheli Duarte de Paula Costa

Micheli Duarte de Paula Costaa, Morena Millsa, Anthony J. Richardsond, Richard A. Fullera, José H. Muelbertb, Hugh P. Possingham.

  • School of Biological Sciences, The University of Queensland, Brisbane, Qld 4072, Australia; m.duartedepaulacost@uq.edu.au; m.mills@imperial.ac.uk; r.fuller@uq.edu.au; h.possingham@uq.edu.au
  • Laboratório de Ecologia do Ictioplâncton, Instituto de Oceanografia, Universidade Federal do Rio Grande, Campus Carreiros, Avenida Itália Km 8, CP 474, 96201900, Rio Grande, RS, Brazil; docjhm@furg.br
  • Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, SL5 7PY, UK
  • Commonwealth Scientific and Industrial Research Organization (CSIRO) Oceans and Atmosphere, Queensland BioSciences Precint (QBP), St. Lucia, QLD, 4072, Australia; anthony.richardson@csiro.au
  • School of Mathematics and Physics, University of Queensland, St. Lucia, QLD 4072, Australia
  • Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
  • The Nature Conservancy, South Brisbane, Queensland 4101, Australia


Created with images by Rafael_Neddermeyer - "boat litoral fishermen" • Erwan Hesry - "Waiting a fisherman to catch lobsters and crab"

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