Genetic analysis reveals harvested Lethrinus nebulosus in the Southwest Indian Ocean comprise two cryptic species
- Healey, Amy J E, Gouws, Gavin, Fennessy, Sean T, Kuguru, Baraka, Sauer, Warwick H H, Shaw, Paul W, McKeown, Niall J
- Authors: Healey, Amy J E , Gouws, Gavin , Fennessy, Sean T , Kuguru, Baraka , Sauer, Warwick H H , Shaw, Paul W , McKeown, Niall J
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124538 , vital:35626 , https://doi.10.1093/icesjms/fsx245
- Description: This study initially aimed to investigate the genetic population/stock structuring of Lethrinus nebulosus in the Southwest Indian Ocean (SWIO) to inform management practices in light of emerging evidence of overharvesting of this species throughout its distribution. Adult samples were genotyped for 14 nuclear microsatellites and by sequencing fragments of the mtDNA control region and COI gene. A salient feature of the data was the congruent cyto-nuclear partitioning of samples into two high divergent, reciprocally monophyletic groups. This indicates that despite no a priori evidence, hitherto described L. nebulosus in the SWIO comprises two cryptic species that co-occur among southern samples. This intermingling indicates that, at least in southern samples, both species are being indiscriminately harvested, which may severely compromise sustainability. Limited microsatellite differentiation was detected within both species, though there was some evidence of isolation in the Mauritian population. In contrast, mtDNA revealed a pattern consistent with chaotic genetic patchiness, likely promoted by stochastic recruitment, which may necessitate a spatial bet-hedging approach to management to satisfy fishery management and conservation goals.
- Full Text:
- Date Issued: 2018
- Authors: Healey, Amy J E , Gouws, Gavin , Fennessy, Sean T , Kuguru, Baraka , Sauer, Warwick H H , Shaw, Paul W , McKeown, Niall J
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124538 , vital:35626 , https://doi.10.1093/icesjms/fsx245
- Description: This study initially aimed to investigate the genetic population/stock structuring of Lethrinus nebulosus in the Southwest Indian Ocean (SWIO) to inform management practices in light of emerging evidence of overharvesting of this species throughout its distribution. Adult samples were genotyped for 14 nuclear microsatellites and by sequencing fragments of the mtDNA control region and COI gene. A salient feature of the data was the congruent cyto-nuclear partitioning of samples into two high divergent, reciprocally monophyletic groups. This indicates that despite no a priori evidence, hitherto described L. nebulosus in the SWIO comprises two cryptic species that co-occur among southern samples. This intermingling indicates that, at least in southern samples, both species are being indiscriminately harvested, which may severely compromise sustainability. Limited microsatellite differentiation was detected within both species, though there was some evidence of isolation in the Mauritian population. In contrast, mtDNA revealed a pattern consistent with chaotic genetic patchiness, likely promoted by stochastic recruitment, which may necessitate a spatial bet-hedging approach to management to satisfy fishery management and conservation goals.
- Full Text:
- Date Issued: 2018
Genomic analysis reveals multiple mismatches between biological and management units in yellowfin tuna (Thunnus albacares)
- Mullins, Rachel B, McKeown, Niall J, Sauer, Warwick H H, Shaw, Paul W
- Authors: Mullins, Rachel B , McKeown, Niall J , Sauer, Warwick H H , Shaw, Paul W
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124549 , vital:35627 , https://doi.10.1093/icesjms/fsy102
- Description: The South African (SAF) yellowfin tuna (Thunnus albacares) fishery represents a potential example of misalignment between management units and biological processes. The SAF fishery spans an operational stock with a boundary at 20_E, either side of which fish are considered part of Atlantic or Indian Ocean regional stocks. However, the actual recruitment of fish from Atlantic and Indian Ocean spawning populations into SAF waters is unknown. To address this knowledge gap, genomic analysis (11 101 SNPs) was performed on samples from Atlantic and Indian Ocean spawning sites, including SAF sites spanning the current stock boundary. Outlier loci conferred high discriminatory power to assignment tests and revealed that all SAF fish were assigned to the Indian Ocean population and that no Atlantic Ocean fish appeared in the SAF samples. Additionally, several Indian Ocean migrants were detected at the Atlantic spawning site demonstrating asymmetric dispersal and the occurrence of a mixed-stock fishery in Atlantic waters. This study highlights both the spatial inaccuracy of current stock designations and a misunderstanding of interactions between the underlying biological units, which must be addressed in light of local and global declines of the species. Specifically, the entire SAF fishery must be managed as part of the Indian Ocean stock.
- Full Text:
- Date Issued: 2018
- Authors: Mullins, Rachel B , McKeown, Niall J , Sauer, Warwick H H , Shaw, Paul W
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124549 , vital:35627 , https://doi.10.1093/icesjms/fsy102
- Description: The South African (SAF) yellowfin tuna (Thunnus albacares) fishery represents a potential example of misalignment between management units and biological processes. The SAF fishery spans an operational stock with a boundary at 20_E, either side of which fish are considered part of Atlantic or Indian Ocean regional stocks. However, the actual recruitment of fish from Atlantic and Indian Ocean spawning populations into SAF waters is unknown. To address this knowledge gap, genomic analysis (11 101 SNPs) was performed on samples from Atlantic and Indian Ocean spawning sites, including SAF sites spanning the current stock boundary. Outlier loci conferred high discriminatory power to assignment tests and revealed that all SAF fish were assigned to the Indian Ocean population and that no Atlantic Ocean fish appeared in the SAF samples. Additionally, several Indian Ocean migrants were detected at the Atlantic spawning site demonstrating asymmetric dispersal and the occurrence of a mixed-stock fishery in Atlantic waters. This study highlights both the spatial inaccuracy of current stock designations and a misunderstanding of interactions between the underlying biological units, which must be addressed in light of local and global declines of the species. Specifically, the entire SAF fishery must be managed as part of the Indian Ocean stock.
- Full Text:
- Date Issued: 2018
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