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Matich P, Plumlee JD, Bubley W, Curtis TH, Drymon JM, Mullins LL, Shipley ON, TinHan TC, Fisher MR. Long-term effects of climate change on juvenile bull shark migratory patterns. J Anim Ecol 2024. [PMID: 39016072 DOI: 10.1111/1365-2656.14140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Accepted: 04/08/2024] [Indexed: 07/18/2024]
Abstract
Seasonal variability in environmental conditions is a strong determinant of animal migrations, but warming temperatures associated with climate change are anticipated to alter this phenomenon with unknown consequences. We used a 40-year fishery-independent survey to assess how a changing climate has altered the migration timing, duration and first-year survival of juvenile bull sharks (Carcharhinus leucas). From 1982 to 2021, estuaries in the western Gulf of Mexico (Texas) experienced a mean increase of 1.55°C in autumn water temperatures, and delays in autumn cold fronts by ca. 0.5 days per year. Bull shark migrations in more northern estuaries concomitantly changed, with departures 25-36 days later in 2021 than in 1982. Later, migrations resulted in reduced overwintering durations by up to 81 days, and the relative abundance of post-overwintering age 0-1 sharks increased by >50% during the 40-year study period. Yet, reductions in prey availability were the most influential factor delaying migrations. Juvenile sharks remained in natal estuaries longer when prey were less abundant. Long-term declines in prey reportedly occurred due to reduced spawning success associated with climate change based on published reports. Consequently, warming waters likely enabled and indirectly caused the observed changes in shark migratory behaviour. As water temperatures continue to rise, bull sharks in the north-western Gulf of Mexico could forgo their winter migrations in the next 50-100 years based on current trends and physiological limits, thereby altering their ecological roles in estuarine ecosystems and recruitment into the adult population. It is unclear if estuarine food webs will be able to support changing residency patterns as climate change affects the spawning success of forage species. We expect these trends are not unique to the western Gulf of Mexico or bull sharks, and migratory patterns of predators in subtropical latitudes are similarly changing at a global scale.
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Affiliation(s)
- Philip Matich
- Saving the Blue, Cooper City, Florida, USA
- Marine Biology Department, Texas A&M University Galveston, Galveston, Texas, USA
| | - Jeffrey D Plumlee
- School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
| | - Walter Bubley
- Marine Resources Division, South Carolina Department of Natural Resources, Charleston, South Carolina, USA
| | - Tobey H Curtis
- Atlantic Highly Migratory Species Management Division, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Gloucester, Massachusetts, USA
| | - J Marcus Drymon
- Coastal Research and Extension Center, Mississippi State University, Biloxi, Mississippi, USA
- Mississippi-Alabama Sea Grant Consortium, Ocean Springs, Mississippi, USA
| | - Lindsay L Mullins
- Coastal Research and Extension Center, Mississippi State University, Biloxi, Mississippi, USA
- Northern Gulf Institute, Starkville, Mississippi, USA
| | - Oliver N Shipley
- School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York, USA
| | - Thomas C TinHan
- Pacific Islands Ocean Observing System, University of Hawai'i at Mānoa, Honolulu, Hawaii, USA
| | - Mark R Fisher
- Coastal Fisheries Division, Texas Parks and Wildlife Department, Rockport Marine Science Laboratory, Rockport, Texas, USA
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Eustache KB, van Loon E, Rummer JL, Planes S, Smallegange I. Spatial and temporal analysis of juvenile blacktip reef shark (Carcharhinus melanopterus) demographies identifies critical habitats. JOURNAL OF FISH BIOLOGY 2024; 104:92-103. [PMID: 37726231 DOI: 10.1111/jfb.15569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 09/14/2023] [Accepted: 09/17/2023] [Indexed: 09/21/2023]
Abstract
Reef shark species have undergone sharp declines in recent decades, as they inhabit coastal areas, making them an easy target in fisheries (i.e., sharks are exploited globally for their fins, meat, and liver oil) and exposing them to other threats (e.g., being part of by-catch, pollution, and climate change). Reef sharks play a critical role in coral reef ecosystems, where they control populations of smaller predators and herbivorous fishes either directly via predation or indirectly via behavior, thus protecting biodiversity and preventing potential overgrazing of corals. The urgent need to conserve reef shark populations necessitates a multifaceted approach to policy at local, federal, and global levels. However, monitoring programmes to evaluate the efficiency of such policies are lacking due to the difficulty in repeatedly sampling free-ranging, wild shark populations. Over nine consecutive years, we monitored juveniles of the blacktip reef shark (Carcharhinus melanopterus) population around Moorea, French Polynesia, and within the largest shark sanctuary globally, to date. We investigated the roles of spatial (i.e., sampling sites) and temporal variables (i.e., sampling year, season, and month), water temperature, and interspecific competition on shark density across 10 coastal nursery areas. Juvenile C. melanopterus density was found to be stable over 9 years, which may highlight the effectiveness of local and likely federal policies. Two of the 10 nursery areas exhibited higher juvenile shark densities over time, which may have been related to changes in female reproductive behavior or changes in habitat type and resources. Water temperatures did not affect juvenile shark density over time as extreme temperatures proven lethal (i.e., 33°C) in juvenile C. melanopterus might have been tempered by daily variation. The proven efficiency of time-series datasets for reef sharks to identify critical habitats (having the highest juvenile shark densities over time) should be extended to other populations to significantly contribute to the conservation of reef shark species.
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Affiliation(s)
- Kim B Eustache
- PSL Research University, EPHE-UPVD-CNRS, UAR 3278 CRIOBE, Université de Perpignan, Perpignan Cedex, France
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands
| | - Emiel van Loon
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands
| | - Jodie L Rummer
- Australian Research Council Centre of Excellence for Coral Reef Studies and the College of Science and Engineering James Cook University, Townsville, Queensland, Australia
| | - Serge Planes
- PSL Research University, EPHE-UPVD-CNRS, UAR 3278 CRIOBE, Université de Perpignan, Perpignan Cedex, France
- Laboratoire d'Excellence "CORAIL," EPHE, PSL Research University, UPVD, CNRS, UAR 3278 CRIOBE, Papetoai, French Polynesia
| | - Isabel Smallegange
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, UK
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Swift DG, O'Leary SJ, Grubbs RD, Frazier BS, Fields AT, Gardiner JM, Drymon JM, Bethea DM, Wiley TR, Portnoy DS. Philopatry influences the genetic population structure of the blacktip shark (Carcharhinus limbatus) at multiple spatial scales. Mol Ecol 2023; 32:4953-4970. [PMID: 37566208 DOI: 10.1111/mec.17096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 07/22/2023] [Accepted: 07/28/2023] [Indexed: 08/12/2023]
Abstract
Understanding how interactions among microevolutionary forces generate genetic population structure of exploited species is vital to the implementation of management policies that facilitate persistence. Philopatry displayed by many coastal shark species can impact gene flow and facilitate selection, and has direct implications for the spatial scales of management. Here, genetic structure of the blacktip shark (Carcharhinus limbatus) was examined using a mixed-marker approach employing mitochondrial control region sequences and 4339 SNP-containing loci generated using ddRAD-Seq. Genetic variation was assessed among young-of-the-year sampled in 11 sites in waters of the United States in the western North Atlantic Ocean, including the Gulf of Mexico. Spatial and environmental analyses detected 68 nuclear loci putatively under selection, enabling separate assessments of neutral and adaptive genetic structure. Both mitochondrial and neutral SNP data indicated three genetically distinct units-the Atlantic, eastern Gulf, and western Gulf-that align with regional stocks and suggest regional philopatry by males and females. Heterogeneity at loci putatively under selection, associated with temperature and salinity, was observed among sites within Gulf units, suggesting local adaptation. Furthermore, five pairs of siblings were identified in the same site across timescales corresponding with female reproductive cycles. This indicates that females re-used a site for parturition, which has the potential to facilitate the sorting of adaptive variation among neighbouring sites. The results demonstrate differential impacts of microevolutionary forces at varying spatial scales and highlight the importance of conserving essential habitats to maintain sources of adaptive variation that may buffer species against environmental change.
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Affiliation(s)
- Dominic G Swift
- Marine Genomics Laboratory, Department of Life Sciences, Texas A&M University-Corpus Christi, Corpus Christi, Texas, USA
| | - Shannon J O'Leary
- Marine Genomics Laboratory, Department of Life Sciences, Texas A&M University-Corpus Christi, Corpus Christi, Texas, USA
- Department of Biology, Saint Anselm College, Manchester, New Hampshire, USA
| | - R Dean Grubbs
- Florida State University Coastal and Marine Laboratory, St. Teresa, Florida, USA
| | - Bryan S Frazier
- South Carolina Department of Natural Resources, Marine Resources Research Institute, Charleston, South Carolina, USA
| | - Andrew T Fields
- Marine Genomics Laboratory, Department of Life Sciences, Texas A&M University-Corpus Christi, Corpus Christi, Texas, USA
| | - Jayne M Gardiner
- Division of Natural Sciences, New College of Florida, Sarasota, Florida, USA
| | - J Marcus Drymon
- Coastal Research and Extension Center, Mississippi State University, Biloxi, Mississippi, USA
- Mississippi-Alabama Sea Grant Consortium, Ocean Springs, Mississippi, USA
| | - Dana M Bethea
- NOAA Fisheries, U.S. Department of Commerce, Southeast Regional Office, Interagency Cooperation Branch, Protected Resources Division, St. Petersburg, Florida, USA
| | - Tonya R Wiley
- Havenworth Coastal Conservation, Palmetto, Florida, USA
| | - David S Portnoy
- Marine Genomics Laboratory, Department of Life Sciences, Texas A&M University-Corpus Christi, Corpus Christi, Texas, USA
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Matich P, Bigelow CL, Chambers B, Dodds JJ, Hebert JA, Lemieux A, Pittman CM, Trapp J, Bianco B, Cadena CP, Castillo EI, Castillo GI, Dawdy A, Dominguez AI, Dominique N, French DR, Glenn CF, Jackson ECH, Johnson B, Kohl G, Manka C, Martin JK, Pappas M, Reedholm AJ, Snead KM, Tyree MK, Fisher M. Delineation of blacktip shark (Carcharhinus limbatus) nursery habitats in the north-western Gulf of Mexico. JOURNAL OF FISH BIOLOGY 2022; 101:236-248. [PMID: 35591772 DOI: 10.1111/jfb.15103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
Coevolution with predators leads to the use of low-risk habitats by many prey species, which promotes survival during early developmental phases. These nurseries are valued by conservation and management agencies because of their contributions to adult populations. However, the physical and geographic characteristics, like shallow depths and isolation from other marine habitats, that restrict access to predators and thereby reduce risk to juvenile animals can also limit scientific research. Consequently, many nursery habitats are still unidentified and understudied. Here we used gillnet monitoring from 1982 to 2018 to delineate blacktip shark (Carcharhinus limbatus) nurseries in the north-western Gulf of Mexico and elucidated their physical, environmental and biological characteristics. Nursery habitats within estuaries (<2% of spatial area) were proximate to the Gulf of Mexico and exhibited significantly lower variability in salinity than non-nurseries. However, relative abundances of predators and prey were not significant delineators of nursery habitats. As such, food and risk may not influence juvenile blacktip habitat use as expected. Alternatively, reduced osmoregulatory stress attributed to predictable environments likely provides advantageous conditions for blacktips to develop foraging and antipredator tactics, which is vital prior to the winter migration of juvenile sharks into the Gulf of Mexico.
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Affiliation(s)
| | - Camryn L Bigelow
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Barrett Chambers
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Jillian J Dodds
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Jessica A Hebert
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Alexis Lemieux
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Christy M Pittman
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Julianna Trapp
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Brooke Bianco
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Carolina P Cadena
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Emily I Castillo
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Gabriela I Castillo
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Alexandra Dawdy
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Alina I Dominguez
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Nicholas Dominique
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Donavon R French
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Callie F Glenn
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Elena C H Jackson
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Breidon Johnson
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Gunnar Kohl
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Cameron Manka
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Jared K Martin
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Matthew Pappas
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Audrey J Reedholm
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Kailey M Snead
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Matthew K Tyree
- Marine Biology Department, Texas A & M University at Galveston, Galveston, Texas, USA
| | - Mark Fisher
- Texas Parks and Wildlife Department, Coastal Fisheries Division, Rockport Marine Science Laboratory, Rockport, Texas, USA
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