UHI Research Database pdf download summary Issues around fisheries for small pelagic fish Fox, Clive Publication date: 2014 The re-use license for this item is: CC BY-NC-SA The Document Version you have downloaded here is: Publisher's PDF, also known as Version of record Link to author version on UHI Research Database Citation for published version (APA): Fox, C. (2014). Issues around fisheries for small pelagic fish. (SAMS Internal Reports). SAMS. 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Oct. 2021 Issues around fisheries for small pelagic fish Clive J Fox Scottish Association for Marine Science Scottish Marine Institute Dunstaffnage, Oban United Kingdom PA371QA SAMS Internal Reports, No. 284 1 Citation This work was partially funded by FAO, Rome as part of their internal report series. It is reproduced here with their permission and should be cited as:- Fox, C.J. (2014) Issues around fisheries for small pelagic fish. SAMS Internal Report, 284, 260 pp. Copyright statement This work was created for educational purposes under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Unported License This work contains images which are themselves licenced under Creative Commons, before re-use of images in this report please check the original copyright coding which applies. 2 Executive summary This review examines the role of “small pelagic fish” (SPF), and their fisheries, in marine ecosystems. The term “small pelagic fish” is a loose definition usually taken to include small to intermediate-sized species which live mainly in the water column. An alternate term sometimes used is “forage fish”, generally taken to include those species which feed largely on zooplankton and phytoplankton and thus form important trophic links in many marine food-webs. However other workers have questioned the use of this term since most small fish are preyed upon by other (often larger) members of marine foodwebs. Many of the SPF species form large schools and this makes them attractive targets for fisheries. SPF thus find a wide range of uses for humans including direct consumption (as fresh or preserved fish) and as raw materials for processing into fish meals and oils (Alder and Pauly 2006). A significant proportion is also used in production of pet foods and a smaller fraction of raw oil around 200 Kt is processed into health supplements (Shepherd and Jackson 2013). The demand for both fresh, preserved and reduction products derived from SPF is growing as human population increases and affluent societies increasingly focus on “healthy” diets. There are also trends for increased demand for perceived “high-status” foods, such as Atlantic salmon (the majority of which is farmed) and tuna from countries such as China. Whilst some farmed fish species do not have a requirement for marine fish oils in the diet, species such as Atlantic salmon do. Tuna fattening has also emerged as a relatively recent aquaculture activity which is generating increasing demands for small-fish to use as fresh feed. Trends in consumer buying power are likely to continue to fuel increasing demand for these products but, unless alternative feed sources can be found, continued growth of these sectors may be unsustainable. As in other areas of fisheries management, the key challenge will be managing SPF fisheries in a manner that meets as much human demand as possible, whilst not depleting the stocks themselves or impacting other components of the marine food-webs which rely on these species as prey. Many SPF species mature relatively young and have high potential rates of population increase so that, based on their life-history characteristics, they can be classified as generally having low vulnerability (Tables 1-3). However, this does not mean that their populations cannot be seriously depleted by over-fishing when other environmental, ecological, behavioural and socio-economic factors are taken into account. Whether SPF stocks are more or less susceptible to collapses compared with other longer-lived species has been debated. Mullon et al. (2005) suggested they were slightly less likely (23% of herring and anchovy had collapsed at some point compared with 31% for demersals and 33% for salmon-trouts). Pinsky et al. (2011) reached a slightly different conclusion using a different analysis approach and found that SPF stocks were statistically as likely to have suffered collapses as stocks of larger and longer-lived species. The life history characteristics of SPF certainly mean that their populations often respond quickly to environmental fluctuations leading to rapid changes in abundance. If this is combined with a failure to match fishing capacity to production and to control fishing pressure rapidly enough when the productivity of the stocks 3 declines, stock collapse is likely to occur. Well-known examples include Peruvian anchoveta, Californian sardine and North Sea herring stocks. On the positive side, the life history characteristics of SPF mean that they can often recover relatively rapidly from over- exploitation as long as environmental conditions also improve, a conclusion which appears to be borne out by experience with several stocks e.g. North Sea herring. The recruitment (numbers of young fish surviving to enter the fishery) dynamics of SPF have long fascinated scientists leading to several classic recruitment control theories such as the “stable-ocean” and “window-of-opportunity” hypotheses. However, the range of potential factors affecting egg and larval survival combined with the temporal and spatial complexity of the ecosystems involved has meant that a full understanding of the mechanisms controlling “year-class strength” has remained elusive. Despite considerable effort in developing both statistical recruitment-environment models and coupled biological- oceanographic models, forecast skill remains rather limited and the forecast time-horizon tends to be too short to be of great assistance in medium to long-term fisheries planning. Given that we cannot forecast SPF recruitment with sufficient skill, assessment tools capable of tracking rapid shifts in stock productivity are required. Techniques such as larval abundance and acoustics surveys are therefore often employed but management processes need to be responsive to changes in productivity at appropriate timescales. The main lesson from the major global SPF collapses is that excess fishing and processing capacity should not be allowed to develop because it inevitably proves extremely difficult to cut back. The increasing worldwide emphasis on “ecosystem-based approaches to fisheries management” also implies that trophic interactions of SPF need to be taken into account. The overall goal of EAFM is to ensure that fisheries do not compromise the wider biodiversity and functioning of marine ecosystems. Many SPF are important prey for other fish, birds and marine mammals and in some cases changes in SPF abundance have been shown to directly impact breeding success e.g. in penguins and black-legged kittiwake. SPF also provide vital nutrition for other fish which are themselves of commercial value e.g. many gadiods, Atlantic and Pacific salmon. Recent analyses have compared the economic value of direct catches of SPF against their economic value as prey for other fish which are commercially harvested. These results suggest that the potential value of SPF as prey should be taken into account when designing harvest strategies. Successful EAFM would also therefore help ensure long- term fisheries sustainability across a broader range of species. Many authors have considered that EAFM requires a shift away from traditional single-species management, at least as it has been commonly practiced in North America and Europe. However, implementing multi- species assessments remains a challenge because marine foodwebs are rarely fully characterised and models such as ECOPATH and ECOSIM have relatively high data demands. In some cases, where the fisheries are focussed largely on a restricted number of forage species, implementation of EAFM may be easier. Operational examples include the Baltic, Peruvian up-welling and Benguela. Even in these situations running multi-species models annually is challenging resulting in the development of ad hoc rules e.g. one-third for the birds. In many sub-tropical and tropical ecosystems, such detailed data are not available 4 (the main “forage” species caught are often not reported to species level because of difficulties in taxonomy and lack of local expertise and resources). Analysis of the current status of SPF stocks globally shows widely varying results – some stocks are in a healthy state and are being sustainably fished whilst others are depleted. A lack of data on stock