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Fernández-Corredor E, Francotte L, Martino I, Fernández-Álvarez FÁ, García-Barcelona S, Macías D, Coll M, Ramírez F, Navarro J, Giménez J. Assessing juvenile swordfish (Xiphias gladius) diet as an indicator of marine ecosystem changes in the northwestern Mediterranean Sea. MARINE ENVIRONMENTAL RESEARCH 2023; 192:106190. [PMID: 37820479 DOI: 10.1016/j.marenvres.2023.106190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 08/31/2023] [Accepted: 09/15/2023] [Indexed: 10/13/2023]
Abstract
To preserve marine biodiversity, we need reliable early warning indicators that inform changes in marine ecosystems. As reliable samplers of mid-trophic level communities, studying the trophodynamics of large pelagic fish can contribute to monitoring these changes. Here, we combined stomach content and stable isotope analyses to reconstruct the diet of juvenile swordfish (Xiphias gladius) in the northwestern Mediterranean Sea, in a time-lapse of almost a decade (2012 and 2020). Overall, our study showed that swordfish fed on a wide range of fish and cephalopod species from both pelagic and demersal habitats. A dietary shift towards increasing consumption of cephalopods and decreasing consumption of Gadiformes had been observed between 2012 and 2020. Stable isotope approaches revealed that gelatinous organisms were also important prey, particularly for smaller-sized swordfish. We underline the importance of combining multiple and complementary approaches to better reconstruct the diet of generalist species. Our findings highlight the generalist and opportunistic diet of Mediterranean swordfish, which makes them good candidates for monitoring changes in the ecosystem.
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Affiliation(s)
| | - Luca Francotte
- Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
| | - Ilaria Martino
- Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
| | | | | | - David Macías
- Centro Oceanográfico de Málaga (IEO-CSIC), Fuengirola, Spain
| | - Marta Coll
- Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain; Ecopath International Initiative (EII), Barcelona, Spain
| | | | - Joan Navarro
- Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
| | - Joan Giménez
- Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
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Tracey SR, Wolfe BW, Hartmann K, Pepperell J, Williams SM. Movement behavior of swordfish provisions connectivity between the temperate and tropical southwest Pacific Ocean. Sci Rep 2023; 13:11812. [PMID: 37479745 PMCID: PMC10362066 DOI: 10.1038/s41598-023-38744-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/13/2023] [Indexed: 07/23/2023] Open
Abstract
Swordfish (Xiphias gladius) are a widely distributed (45°N-45°S) large pelagic fish targeted by fisheries worldwide. Swordfish that occur at high latitudes tend to disproportionately be large adults, so their movements have implications for population dynamics and fisheries management. In the southwest Pacific, little is known about this subset of the stock and existing evidence suggests limited movement from the subtropics into cooler high latitude waters. Here, we capitalize on the recent emergence of a recreational swordfish fishery off temperate southeast Australia to characterize movements of swordfish caught in the fishery with pop-up satellite archival transmitting tags. Data were recovered from tags deployed for 56-250 days on 11 swordfish (50-350 kg) tagged between 38 and 43°S in the western Tasman Sea. Five swordfish entered the Coral Sea (< 30°S), with four reaching north to 11-24°S, up to 3275 km away from location of capture. Behavior modelling suggests these four individuals rapidly transited north until encountering 23-27 °C water, at which point they lingered in the area for several months, consistent with spawning-related partial migration. One migrating swordfish still carrying a tag after the spawning season returned to ~ 120 km of its release location, suggesting site fidelity. Movements toward the central south Pacific were confined to two individuals crossing 165°E. Swordfish predominantly underwent normal diel vertical migration, descending into the mesopelagic zone at dawn (median daytime depth 494.9 m, 95% CI 460.4-529.5 m). Light attenuation predicted daytime depth, with swordfish rising by up to 195 m in turbid water. At night, swordfish were deeper during the full moon, median night-time depth 45.8 m (37.8-55.5) m versus 18.0 m (14.9-21.8) m at new moon. Modelling fine-scale (10 min-1) swordfish depth revealed dynamic effects of moon phase varying predictably across time of night with implications for fisheries interactions. Studying highly migratory fishes near distribution limits allows characterization of the full range of movement phenotypes within a population, a key consideration for important fish stocks in changing oceans.
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Affiliation(s)
- Sean R Tracey
- Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, Hobart, TAS, 7001, Australia.
| | - Barrett W Wolfe
- Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, Hobart, TAS, 7001, Australia
| | - Klaas Hartmann
- Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, Hobart, TAS, 7001, Australia
| | - Julian Pepperell
- Pepperell Research and Consulting Pty Ltd, P.O. Box 1475, Noosaville DC, QLD, 4566, Australia
| | - Sam M Williams
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia
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Preti A, Stohs SM, DiNardo GT, Saavedra C, MacKenzie K, Noble LR, Jones CS, Pierce GJ. Feeding ecology of broadbill swordfish (Xiphias gladius) in the California current. PLoS One 2023; 18:e0258011. [PMID: 36795680 PMCID: PMC9934375 DOI: 10.1371/journal.pone.0258011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 10/17/2022] [Indexed: 02/17/2023] Open
Abstract
The feeding ecology of broadbill swordfish (Xiphias gladius) in the California Current was described based on analysis of stomach contents collected by fishery observers aboard commercial drift gillnet boats from 2007 to 2014. Prey were identified to the lowest taxonomic level and diet composition was analyzed using univariate and multivariate methods. Of 299 swordfish sampled (74 to 245 cm eye-to-fork length), 292 non-empty stomachs contained remains from 60 prey taxa. Genetic analyses were used to identify prey that could not be identified visually. Diet consisted mainly of cephalopods but also included epipelagic and mesopelagic teleosts. Jumbo squid (Dosidicus gigas) and Gonatopsis borealis were the most important prey based on the geometric index of importance. Swordfish diet varied with body size, location and year. Jumbo squid, Gonatus spp. and Pacific hake (Merluccius productus) were more important for larger swordfish, reflecting the ability of larger specimens to catch large prey. Jumbo squid, Gonatus spp. and market squid (Doryteuthis opalescens) were more important in inshore waters, while G. borealis and Pacific hake predominated offshore. Jumbo squid was more important in 2007-2010 than in 2011-2014, with Pacific hake being the most important prey item in the latter period. Diet variation by area and year probably reflects differences in swordfish preference, prey availability, prey distribution, and prey abundance. The range expansion of jumbo squid that occurred during the first decade of this century may particularly explain their prominence in swordfish diet during 2007-2010. Some factors (swordfish size, area, time period, sea surface temperature) that may influence dietary variation in swordfish were identified. Standardizing methods could make future studies more comparable for conservation monitoring purposes.
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Affiliation(s)
- Antonella Preti
- Institute of Marine Studies, University of California Santa Cruz, Santa Cruz, California, United States of America
- Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom
- NOAA Fisheries, Southwest Fisheries Science Center, La Jolla, California, United States of America
- * E-mail:
| | - Stephen M. Stohs
- NOAA Fisheries, Southwest Fisheries Science Center, La Jolla, California, United States of America
| | - Gerard T. DiNardo
- SCS Global Services, Emeryville, California, United States of America
| | - Camilo Saavedra
- Centro Oceanográfico de Vigo, Instituto Español de Oceanografía, Vigo, Spain
| | - Ken MacKenzie
- Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom
| | - Leslie R. Noble
- Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway
| | - Catherine S. Jones
- Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom
| | - Graham J. Pierce
- Instituto de Investigaciones Marinas, Vigo, Spain
- Oceanlab, University of Aberdeen, Newburgh, Aberdeenshire, Scotland, United Kingdom
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