Browsing by Author "Hilborn, Ray"

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    Escaping the tyranny of the grid: a more realistic way of defining fishing opportunities
    (NRC Research Press, 2005) Branch, Trevor A; Hilborn, Ray; Bogazzi, Eugenia
    A large part of fishing behavior is choosing where to fish. Trawl skippers usually choose between known fishing opportunities, which are observed as groups of trawls that are conducted in the same portion of a fishing ground, or go exploratory fishing. We outline a simple clustering method based on Euclidean distances between trawls that offers a more realistic way of defining fishing opportunities than grid cells or statistical areas. The resulting cluster tree of trawls is divided into individual groups of trawls (fishing opportunities) using a recommended cut point. Our method correctly classified simulated trawls into fishing opportunities. Fishing opportunities were obtained for vessels in the British Columbia groundfish trawl fishery; each vessel usually fished at a wide variety (mean 26, standard deviation 16, range 2 69) of fishing opportunities. Within each fishing opportunity, trawls generally caught similar species. In the Argentina scallop fishery, our method was able to divide exploratory from regular fishing trawls, with obvious applications for catch-per-unit-effort calculations. Our method could also be used to detect positional errors in data from these fisheries. Fishing opportunities could provide indications of how fishermen might react to marine protected areas and to the imposition of quotas on multispecies fisheries.
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    Fleet dynamics and behavior:lessons for fisheries management
    (NRC Research Press, 2011) Branch, Trevor A; Hilborn, Ray; Haynie, Alan C; Fay, Gavin; Flynn, Lucy; Griffiths, Jennifer; Marshall, Kristin N; Randall, Jeffrey K; Scheuerell, Jennifer M; Ward, Eric J; Young, Mark
    We review fleet dynamics and fishermen behavior from an economic and sociological basis in developing fisheries, in mature fisheries near full exploitation, and in senescent fisheries that are overexploited and overcapitalized. In all cases, fishing fleets behave rationally within the imposed regulatory structures. Successful, generalist fishermen who take risks often pioneer developing fisheries. At this stage, regulations and subsidies tend to encourage excessive entry and investments, creating the potential for serial depletion. In mature fisheries, regulations often restrict season length, vessel and gear types, fishing areas, and fleet size, causing or exacerbating the race for fish and excessive investment, and are typically unsuccessful except when combined with dedicated access privileges (e.g., territorial rights, individual quotas). In senescent fisheries, vessel buyback programs must account for the fishing power of individuals and their vessels. Subsidies should be avoided as they prolong the transition towards alternative employment. Fisheries managers need to create individual incentives that align fleet dynamics and fishermen behavior with the intended societal goals. These incentives can be created both through management systems like dedicated access privileges and through market forces.
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    Replacing trip limits with individual transferable quotas:implications for discarding
    (Elsevier, 2006) Branch, Trevor A; Rutherford, Kate; Hilborn, Ray
    In the British Columbia groundfish fishery (BC fishery), full observer coverage and the accounting of discard mortality of marketable fish in landing limits resulted in low discard fractions. When individual transferable quotas (ITQs) were additionally introduced, total discard fractions declined for most species, and marketable discard fractions declined from 0.20% to 0.10%, after an adjustment period. In contrast, the US West Coast groundfish fishery, which is regulated by 2-monthly landing limits, has higher discard fractions (31–43% vs. 14–19% for BC). The BC experience suggests that full observer coverage, ITQs, and mortality accounting would reduce West Coast discarding fractions, but severe catch restrictions on overfished West Coast species may limit such reductions.