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Taboada FG, Chust G, Santos Mocoroa M, Aldanondo N, Fontán A, Cotano U, Álvarez P, Erauskin-Extramiana M, Irigoien X, Fernandes-Salvador JA, Boyra G, Uriarte A, Ibaibarriaga L. Shrinking body size of European anchovy in the Bay of Biscay. GLOBAL CHANGE BIOLOGY 2024; 30:e17047. [PMID: 38273534 DOI: 10.1111/gcb.17047] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Revised: 10/21/2023] [Accepted: 10/31/2023] [Indexed: 01/27/2024]
Abstract
Decreased body size is often cited as a major response to ocean warming. Available evidence, however, questions the actual emergence of shrinking trends and the prevalence of temperature-driven changes in size over alternative drivers. In marine fish, changes in food availability or fluctuations in abundance, including those due to size-selective fishing, provide compelling mechanisms to explain changes in body size. Here, based on three decades of scientific survey data (1990-2021), we report a decline in the average body size-length and weight-of anchovy, Engraulis encrasicolus L., in the Bay of Biscay. Shrinking was evident in all age classes, from juveniles to adults. Allometric adjustment indicated slightly more pronounced declines in weight than in total length, which is consistent with a change toward a slender body shape. Trends in adult weight were nonlinear, with rates accelerating to an average decline of up to 25% decade-1 during the last two decades. We found a strong association between higher anchovy abundance and reduced juvenile size. The effect of density dependence was less clear later in life, and temperature became the best predictor of declines in adult size. Theoretical analyses based on a strategic model further suggested that observed patterns are consistent with a simultaneous, opposing effect of rising temperatures on accelerating early growth and decreasing adult size as predicted by the temperature-size rule. Macroecological assessment of ecogeographical-Bergmann's and James'-rules in anchovy size suggested that the observed decline largely exceeds intraspecific variation and might be the result of selection. Limitations inherent in the observational nature of the study recommend caution and a continued assessment and exploration of alternative drivers. Additional evidence of a climate-driven regime shift in the region suggests, however, that shrinking anchovy sizes may signal a long-lasting change in the structure and functioning of the Bay of Biscay ecosystem.
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Affiliation(s)
- Fernando G Taboada
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Guillem Chust
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - María Santos Mocoroa
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Naroa Aldanondo
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Almudena Fontán
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Unai Cotano
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Paula Álvarez
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | | | - Xabier Irigoien
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | | | - Guillermo Boyra
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Andrés Uriarte
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
| | - Leire Ibaibarriaga
- AZTI Marine Research, Basque Research and Technology Alliance (BRTA), Sukarrieta, Spain
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Bolle LJ, Hoek R, Pennock I, Poiesz SSH, van Beusekom JEE, van der Veer HW, Witte JI, Tulp I. No evidence for reduced growth in resident fish species in the era of de-eutrophication in a coastal area in NW Europe. MARINE ENVIRONMENTAL RESEARCH 2021; 169:105364. [PMID: 34087761 DOI: 10.1016/j.marenvres.2021.105364] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 04/04/2021] [Accepted: 05/11/2021] [Indexed: 06/12/2023]
Abstract
Coastal areas in north-western Europe have been influenced by elevated nutrient levels starting in the 1960s. Due to efficient measures, both nitrate and phosphate levels decreased since the mid-1980s. The co-occurring declines in nutrient loadings and fish productivity are often presumed to be causally linked. We investigated whether four resident fish species (twaite shad, bull-rout, thick-lipped grey mullet and eelpout), that spend the majority of their life in the vicinity of the coast, differed in growth between the historic eutrophication period compared to the recent lower nutrient-level period. Based on Von Bertalanffy growth models of length at age, and the analysis of annual otolith increments, we investigated the difference in sex-specific growth patterns and related these to temperature, eutrophication level (Chlorophyll a), growth window and fish density. In all four species, annual otolith growth rates during the early life stages differed between the two periods, mostly resulting in larger lengths at age in the recent period. All species showed significant correlations between increment size and temperature, explaining the observed period differences. The lack of an effect of total fish biomass provided no evidence for density dependent growth. A correlation with chlorophyll was found in bull-rout, but the relationship was negative, thus not supporting the idea of growth enhanced by high nutrient levels. In conclusion, we found no evidence for reduced growth related to de-eutrophication. Our results indicate that temperature rise due to climate change had a greater impact on growth than reduced food availability due to de-eutrophication. We discuss potential consequences of growth changes for length-based indicators used in management.
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Affiliation(s)
- Loes J Bolle
- Wageningen Marine Research, IJmuiden, the Netherlands.
| | - Ruben Hoek
- Wageningen Marine Research, IJmuiden, the Netherlands.
| | - Ineke Pennock
- Wageningen Marine Research, IJmuiden, the Netherlands.
| | - Suzanne S H Poiesz
- NIOZ Royal Netherlands Institute of Sea Research, Den Burg, the Netherlands.
| | | | | | | | - Ingrid Tulp
- Wageningen Marine Research, IJmuiden, the Netherlands.
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