Interannual Variability of Fisheries Economic Returns and Energy Ratios Is Mostly Explained by Gear Type

Abstract

According to portfolio theory applied to fisheries management, economic returns are stabilised by harvesting in a portfolio stocks of species whose returns are negatively correlated and for which the portfolio economic return variance is smaller than the sum of stock specific return variances. Also, variability is expected to decrease with portfolio width. Using a range of indicators, these predictions were tested for the French fishing fleets in the Bay of Biscay (Northeast Atlantic) during the period 2001–2009. For this, vessels were grouped into eight fishing fleets based on the gears used and exploited species were grouped into five functional groups. The portfolio width of fleets ranged from 1–3 functional groups, or 4–19 species. Economic fleet returns (sale revenues minus fishing costs) varied strongly between years; the interannual variability was independent of portfolio width (species or functional groups). Energy ratio expressed by the ratio between fuel energy used for fishing and energy contained in landings varied from 0.3 for purse seines to 9.7 for trawlers using bottom trawls alone or in combination with pelagic trawls independent of portfolio width. Interannual variability in total sale revenues was larger than the sum of species specific sales revenue variability, except for fleets using hooks and pelagic trawlers; it increased with the number of species exploited. In conclusion, the interannual variability of economic returns or energy ratios of French fisheries in the Bay of Biscay did not decrease with the number of species or functional groups exploited, though it varied between fleets.

Thirty years of change and the future of Alaskan fisheries: Shifts in fishing participation and diversification in response to environmental, regulatory and economic pressures

“…Fishers often attempt to mitigate risk by diversifying their portfolios of target species, fishing strategies and livelihood activities (Cinner & Bodin, ; Cunningham, Bennear, & Smith, ; Gentner & Sutton, ; Minnegal & Dwyer, ). Overwhelmingly, the literature on commercial fisheries has shown that diversification can buffer against financial risk (Cline, Schindler, & Hilborn, ; Gourguet et al., ; Hilborn, Maguire, Parma, & Rosenberg, ; Kasperski & Holland, ; Perruso, Weldon, & Larkin, ; Sethi, Reimer, & Knapp, ), with relatively few exceptions (Anderson et al., ; Trenkel, Daurès, Rochet, & Lorance, ; Ward et al., ). For recreational and subsistence fisheries, where the benefits of fishing are not typically measured in terms of economic yield, diversification can be used to maintain the quality of the fishing experience or amount of food harvested (Beaudreau, Chan, & Loring, ; Gentner & Sutton, ; Loring, Gerlach, Atkinson, & Murray, ).…”

Identifying marine pelagic ecosystem management objectives and indicators

“…In contrast to many demersal mixed-species fisheries, pelagic fishing generally targets single species [12], so direct pelagic fishing impacts affect single stocks, though indirect effects may cause food web perturbations [78]. Further, pelagic fisheries do not damage vulnerable benthic habitats and the fisheries exhibit low CO 2 footprints per kg of protein harvested [62] and use little fuel energy per kJ of energy harvested [88]. The strong environmental forcing of recruitment, growth and survival makes for very uncertain biomass reference-points based on the single species stock assessments used in the management of pelagic fish stocks [4,20].…”

“…For example, the UK herring market never recovered after the collapse of North Sea herring [20]. For fishers themselves however, interannual variations in economic returns might be compensated between species [88]. Relative interannual stability of landings is a suitable operational objective for pelagic fisheries, with interannual variation in landings as indicator.…”

How to provide scientific advice for ecosystem‐based management now

“…Economic return is an important indicator for assessing the sustainability of fishing fleets and thus dependent jobs. It can vary between fleets and years due to different factors including variable fuel costs (Trenkel et al., ).…”

“…They differ in details but generally adopt a sizeand traits-based approach, for example Harfoot et al (2014), Jennings andCollingridge (2015), Jacobsen, Burgess, and Andersen (2017). A size or functional group resolution is important given fisheries are size and group selective, with different gears generally targeting different size ranges and species/groups (Daurès, Rochet, Van Iseghem, & Trenkel, 2009;Fauconnet, Trenkel, Morandeau, Caill-Milly, & Rochet, 2015;Trenkel, Daurès, Rochet, & Lorance, 2013). Also, technical measures regulating size selection of fishing gears are an important management tool in many jurisdictions around the world.…”