Last Trip Return Rate Influence Patch Choice Decisions of Small-Scale Shrimp Trawlers: Optimal Foraging in São Francisco, Coastal Brazil

Abstract

Studies using Optimal Foraging Theory to understand human behavior have stated that daily variation in patch profitability could explain mismatches between theoretical predictions and actual behavior. In this paper, we tested whether the return rate of the last fishing trip could predict fishers' choices to return or choose a different fishing ground for their next trip. We collected data on fishing trips using interviews and direct observation of fishers' activities at the main landing point in São Francisco, a small-scale shrimp fishing community on Brazil's southern coast. We found that fishers returned more often to fishing grounds where the return rate of the previous fishing trip was above the average gross return of the environment. Daily variations in patch quality accounted for fishers' decisions, but other factors may also influence the observed behavior, such as scale of analysis, information exchange, environmental conditions, and economic variables.

Navigating Over Space and Time: Fishing Effort Allocation and the Development of Customary Norms in an Open-Access Mangrove Estuary in Ecuador

“…This research shows that a higher fishing effort correlates with a higher CPUE, consistent with the predictions of optimal foraging theories and patch time allocation models (Sosis 2002;Chimello de Oliveira and Begossi 2011;Aswani 1998;Thomas 2007). However, further analysis of individual differentiation over the same space reveals that the same set of individuals habitually harvest less productive areas as spaces they have claimed as "their own."…”

“…They move on to the next most profitable patch when the returns fall below the average. As predicted by optimal foraging theory, fishers alternate fishing grounds based on their knowledge and experience with patch productivity on a previous day (Sosis 2002;Chimello de Oliveira and Begossi 2011).…”

Fishers’ knowledge indicates short-term temporal changes in the amount and composition of catches in the southwestern Atlantic

“…This decline in high valued species was not observed in the southeastern Brazilian coast over the studied timeframe, which further indicated that fishing pressure had not reached critical levels. On the contrary, high valued species were more often mentioned in recent interviews, possibly related to increased exploitation of shrimps and large reef predators, such as groupers and snappers (Lutjanidae) [11,15,41,52]. Other possibility would be that the relative value of these fishing resources increased over time, so fishers interviewed more recently may be applying a more intense fishing effort to catch these fishing resources.…”

Risk sensitivity and the behaviour of fishing vessels

“…For example, Lopes and Begossi (2011) found that the number of trips on a given day was positively correlated with catch on the previous day for small-scale trawlers, while de Olivera and Begossi (2011) found that the return rate on the last fishing trip influenced fishers' choices to return to that fishing ground on their next trip. Following an unprofitable trip, skippers will often remain in port to avoid further losses, typically until conditions affecting the perceived availability of fish (e.g.…”