How a multidisciplinary approach involving ethnoecology, biology and fisheries can help explain the spatio‐temporal changes in marine fish abundance resulting from climate change

Abstract

Predicting the impact of climate change on marine ecosystems or how fish and other species are adapting to rising sea temperatures is still subject to much uncertainty, despite considerable progress in recent years. In this study we assess whether our understanding of the impact of sea warming on marine fish can be enhanced with an interdisciplinary approach that collates data from fisheries, fishermen and scientific research. By doing this, we aim to shed light on the major changes in the abundance and diversity of warm and cold water fish in recent decades in relation to sea warming. Location: This study was conducted in the north-western Mediterranean, where the impacts of global warming are particularly critical because range shifts are physically constrained. Methods: We collected and combined statistical data from fisheries, the traditional ecological knowledge of fishermen (TEK), reproductive data (histological gonad analyses and ichthyoplankton surveys) and extensive research into the relevant literature (including systematic catalogues and museum collections and their databases). Results: We have found that changes in the abundance of fish have followed a particular spatio-temporal sequence, with three different phases of colonization in the case of warm-water species (occasional occurrence, common presence and establishment), and three phases of regression (abundance reduction, range contraction and disappearance from the catch) in the case of cold-water species. Main conclusions: Overall, the results show that this multidisciplinary approach, combining qualitative and quantitative information from different sources, provides new insight into the observed changes in fish diversity and abundance in relation to climate changeThis study was financed by the Abertis Foundation (http://www.fundacioabertis.org/). In addition, J.L. benefited from a Ramon y Cajal Research contract from the Spanish Ministry of Economy and Competitiveness. A.S. was partially supported by the project MAR-CTM2010-1887

Reproductive traits of the pompano, Trachinotus ovatus (Linnaeus, 1758), in the north-western Mediterranean

“…It appears likely, therefore, that the present-day sea warming trends and the associated changes in spawning phenology would give the pompano (and other warm-water fish species) an advantage and favour their successful establishment into new habitats. Therefore, while global warming can benefit warm-water species, allowing their expansion into areas they did not previously occupy (Sabatés et al, 2006;Petitgas et al, 2013;Lloret et al, 2015), it may threaten cold-water species, leading to local extinctions of certain species (Drinkwater, 2005;Perry et al, 2005). In this sense, small increases in temperature might tend to favour recruitment of some species (especially at higher latitudes) but larger temperature increases could lead to recruitment failures (especially at low latitudes) and at times or places where food supply is limited (Munday et al, 2008;Pankhurst & Munday, 2011).…”

“…Meanwhile, for native fish species, small increases in sea temperature during spawning can dramatically increase egg mortality and decrease survivorship to hatching since the egg stage is one of the most thermally sensitive life stages in fish (Rombough, 1997;Gagliano et al, 2007). Changes in the abundance of warm-and cold-water fish species may have farreaching ecosystem effects, such as trophic cascades driven by the local loss/decrease of cold-water predators or by the appearance/increase of warm-water predators (Lloret et al, 2015). Therefore, while global warming can benefit warm-water species, allowing their expansion into areas they did not previously occupy (Sabatés et al, 2006;Petitgas et al, 2013;Lloret et al, 2015), it may threaten cold-water species, leading to local extinctions of certain species (Drinkwater, 2005;Perry et al, 2005).…”

“…However, during the last decade a previously unusual warm-water carangid species, the pompano Trachinotus ovatus has become more frequent in the Gulf of Roses and adjacent waters (southern Gulf of Lyon) (Lloret et al, 2015). However, during the last decade a previously unusual warm-water carangid species, the pompano Trachinotus ovatus has become more frequent in the Gulf of Roses and adjacent waters (southern Gulf of Lyon) (Lloret et al, 2015).…”

Trade‐offs between life‐history traits in a coldwater fish in the Mediterranean Sea: the case of blue whiting Micromesistius poutassou

“…Mediterranean populations of exploited cold‐water species are in a difficult situation because of the specific and synergistic effects of overfishing and climate change (Lloret et al, ). As a result, the north‐western area of the Mediterranean Sea, which has colder waters than the rest, may become a cul‐de‐sac due to the physical barrier to the predicted northerly shifts in distribution ranges (Lejeusne et al, ); the affected species will be unable to escape from suboptimal environmental conditions and therefore suffer physiological stress (Lloret et al, ). Indeed, during the past two decades, landings of M. poutassou in the Mediterranean Sea have fallen from almost 30,000 t to just 2000 t in 2016 (GFCM, ).…”

Life‐history traits of temperate and thermophilic barracudas (Teleostei: Sphyraenidae) in the context of sea warming in the Mediterranean Sea

“…Sphyraena sphyraena is the usual temperate resident species while the larger, thermophilic barracuda ( S . viridensis ) has apparently become more frequent in the Gulf of Roses and adjacent waters (southern Gulf of Lyon) during the last decade; a fact that is possibly attributed to sea warming (Lloret et al , ).…”