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Seasonal Harvest Patterns in Multispecies Fisheries

Birkenbach, Anna M., Cojocaru, Andreea L., Asche, Frank, Guttormsen, Atle G., Smith, Martin D.
Environmental and resource economics 2020 v.75 no.3 pp. 631-655
bioeconomic models, demersal fish, fisheries, markets, mathematical models
Fishers face multidimensional decisions: when to fish, what species to target, and how much gear to deploy. Most bioeconomic models assume single-species fisheries with perfectly elastic demand and focus on inter-seasonal dynamics. In real-world fisheries, vessels hold quotas for multiple species with heterogeneous biological and/or market conditions that vary intra-seasonally. We analyze within-season behavior in multispecies fisheries with individual fishing quotas, accounting for stock aggregations, capacity constraints, and downward-sloping demand. Numerical results demonstrate variation in harvest patterns. We specifically find: (1) harvests for species with downward-sloping demand tend to spread out; (2) spreading harvest of a high-value species can cause lower-value species to be harvested earlier in the season; and (3) harvest can be unresponsive or even respond negatively to biological aggregation when fishers balance incentives in multispecies settings. We test these using panel data from the Norwegian multispecies groundfish fishery and find evidence for all three. We extend the numerical model to account for transitions to management with individual fishing quotas in multispecies fisheries. We show that, under some circumstances, fishing seasons could contract or spread out.