scholarly journals Predator–prey interactions in the face of management regulations: changes in Mediterranean small pelagic species are not due to increased tuna predation

2017 ◽  
Vol 74 (9) ◽  
pp. 1422-1430 ◽  
Author(s):  
Elisabeth Van Beveren ◽  
Jean-Marc Fromentin ◽  
Sylvain Bonhommeau ◽  
Anne-Elise Nieblas ◽  
Luisa Metral ◽  
...  
Keyword(s):  
Prey Species ◽  
Size Structure ◽  
Bluefin Tuna ◽  
Pelagic Fish ◽  
Fish Populations ◽  
Small Pelagic Fish ◽  
Predator Prey ◽  
Atlantic Bluefin Tuna ◽  
Management Measures ◽  
The Face

Recently, the abundance of young Atlantic bluefin tuna (Thunnus thynnus) tripled in the northwestern Mediterranean following effective management measures. We investigated whether its predation on sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) could explain their concurrent size and biomass decline, which caused a fishery crisis. Combining the observed diet composition of bluefin tuna, their modelled daily energy requirements, their population size, and the abundance of prey species in the area, we calculated the proportion of the prey populations that were consumed by bluefin tuna annually over 2011–2013. To assess whether tuna could alter the size structure of the three small pelagic fish populations (anchovy, sardine, and sprat (Sprattus sprattus)), the size distributions of the consumed prey species were compared with those of the wild populations. We estimated that the annual consumption of small pelagic fish by bluefin tuna is less than 2% of the abundance of these populations. Furthermore, size selectivity patterns were not observed. We thus concluded that tuna predation is unlikely to be the main cause of major changes in the small pelagic fish populations from this area.

scholarly journals Atlantic Multidecadal Oscillations drive the basin-scale distribution of Atlantic bluefin tuna

2019 ◽  
Vol 5 (1) ◽  
pp. eaar6993 ◽  
Author(s):  
Robin Faillettaz ◽  
Grégory Beaugrand ◽  
Eric Goberville ◽  
Richard R. Kirby
Keyword(s):  
Climatic Variability ◽  
Atlantic Multidecadal Oscillation ◽  
Bluefin Tuna ◽  
Stock Management ◽  
Atlantic Bluefin Tuna ◽  
Management Measures ◽  
Basin Scale ◽  
Management Plans ◽  
Regional Abundance ◽  
The 1960S

The Atlantic bluefin tuna (hereafter referred to as “bluefin tuna”), one of the world’s most valuable and exploited fish species, has been declining in abundance throughout the Atlantic from the 1960s until the mid-2000s. Following the establishment of drastic management measures, the stock has started to recover recently and, as a result, stakeholders have raised catch quotas by 50% for the period 2017–2020. However, stock assessments still omit the natural, long-term variability in the species distribution. Here, we explore the century-scale fluctuations in bluefin tuna abundance and distribution to demonstrate a prevailing influence of the Atlantic Multidecadal Oscillation (AMO) to provide new insights into both the collapse of the Nordic bluefin tuna fishery circa 1963 and the recent increase in bluefin tuna abundance in the Northeast Atlantic. Our results demonstrate how climatic variability can modulate the distribution of a large migrating species to generate rapid changes in its regional abundance, and we argue that climatic variability must not be overlooked in stock management plans for effective conservation.

The State of the Adriatic Sea Centered on the Small Pelagic Fish Populations

2002 ◽  
Vol 23 (s1) ◽  
pp. 78-91 ◽  
Author(s):  
Massimo Azzali ◽  
Andrea Felice ◽  
Manlio Luna ◽  
Giulio Cosimi ◽  
Flavio Parmiggiani
Keyword(s):  
Adriatic Sea ◽  
Pelagic Fish ◽  
The State ◽  
Fish Populations ◽  
Small Pelagic Fish

scholarly journals Zooplankton mortality effects on the plankton community of the northern Humboldt Current System: sensitivity of a regional biogeochemical model

2021 ◽  
Vol 18 (9) ◽  
pp. 2891-2916
Author(s):  
Mariana Hill Cruz ◽  
Iris Kriest ◽  
Yonss Saranga José ◽  
Rainer Kiko ◽  
Helena Hauss ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Current System ◽  
Fish Predation ◽  
Grazing Pressure ◽  
Pelagic Fish ◽  
Trophic Levels ◽  
Fish Populations ◽  
Biogeochemical Model ◽  
Small Pelagic Fish ◽  
Humboldt Current

Abstract. Small pelagic fish off the coast of Peru in the eastern tropical South Pacific (ETSP) support around 10 % of global fish catches. Their stocks fluctuate interannually due to environmental variability which can be exacerbated by fishing pressure. Because these fish are planktivorous, any change in fish abundance may directly affect the plankton and the biogeochemical system. To investigate the potential effects of variability in small pelagic fish populations on lower trophic levels, we used a coupled physical–biogeochemical model to build scenarios for the ETSP and compare these against an already-published reference simulation. The scenarios mimic changes in fish predation by either increasing or decreasing mortality of the model's large and small zooplankton compartments. The results revealed that large zooplankton was the main driver of the response of the community. Its concentration increased under low mortality conditions, and its prey, small zooplankton and large phytoplankton, decreased. The response was opposite, but weaker, in the high mortality scenarios. This asymmetric behaviour can be explained by the different ecological roles of large, omnivorous zooplankton and small zooplankton, which in the model is strictly herbivorous. The response of small zooplankton depended on the antagonistic effects of mortality changes as well as on the grazing pressure by large zooplankton. The results of this study provide a first insight into how the plankton ecosystem might respond if variations in fish populations were modelled explicitly.

scholarly journals Allometric relations and consequences for feeding in small pelagic fish in the Bay of Biscay

2012 ◽  
Vol 70 (1) ◽  
pp. 232-243 ◽  
Author(s):  
Eneko Bachiller ◽  
Xabier Irigoien
Keyword(s):  
Body Size ◽  
Prey Size ◽  
Pelagic Fish ◽  
The Body ◽  
Large Prey ◽  
Bay Of Biscay ◽  
Small Pelagic Fish ◽  
Predator Prey ◽  
Allometric Relations ◽  
Gape Size

Abstract Bachiller, E. and Irigoien, X. 2013. Allometric relations and consequences for feeding in small pelagic fish in the Bay of Biscay. – ICES Journal of Marine Science, 70:232–243. The body size of fish is an important factor in determining their biology and ecology, as predators eat prey smaller than themselves. Predator mouth size restricts the availability of possible prey. In this paper we provide the allometric relationships of eight common, small pelagic fish species in the Bay of Biscay. In addition, we describe the predator-prey size ratios for different species, and we determine changes in their ratio-based trophic-niche breadth with increasing body size. Results suggest that gape size does not totally determine the predator-prey size ratio distribution, but predators use the entire available prey size range, including the smallest. As they grow they simply incorporate larger prey as their increased gape size permits. Accordingly, a large degree of overlap was found in the diet composition in terms of size and predator-prey ratios, even between fish of different sizes. Of the species studied, only horse mackerels seem to be clearly specialized in relatively large prey.

scholarly journals Zooplankton mortality effects on the plankton community of the Northern Humboldt Current System: Sensitivity of a regional biogeochemical model

2020 ◽  
Author(s):  
Mariana Hill Cruz ◽  
Iris Kriest ◽  
Yonss Saranga José ◽  
Rainer Kiko ◽  
Helena Hauss ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Current System ◽  
Fish Predation ◽  
Grazing Pressure ◽  
Pelagic Fish ◽  
Trophic Levels ◽  
Fish Populations ◽  
Biogeochemical Model ◽  
Small Pelagic Fish ◽  
Humboldt Current

Abstract. Small pelagic fish off the coast of Peru in the Eastern Tropical South Pacific (ETSP) support around 10 % of the global fish catches. Their stocks fluctuate interannually due to environmental variability which can be exacerbated by fishing pressure. Because these fish are planktivorous, any change in fish abundance may directly affect the plankton and the biogeochemical system. To investigate the potential effects of variability in small pelagic fish populations on lower trophic levels, we used a coupled physical-biogeochemical model to build scenarios for the ETSP and compare these against an already published reference simulation. The scenarios mimic changes in fish predation by either increasing or decreasing mortality of the model's large and small zooplankton compartments. The results revealed that large zooplankton was the main driver of the response of the community. Its concentration increased under low mortality conditions and its prey, small zooplankton and large phytoplankton, decreased. The response was opposite, but weaker, in the high mortality scenarios. This asymmetric behaviour can be explained by the different ecological roles of large, omnivorous zooplankton, and small zooplankton, which in the model is strictly herbivorous. The response of small zooplankton depended on the antagonistic effects of mortality changes as well as the grazing pressure by large zooplankton. The results of this study provide a first insight on how the plankton ecosystem might respond if variations in fish populations were modelled explicitly.

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