Age and growth of the Cape knifejaw Oplegnathus conwayi, an endemic South African teleost
- Foster, Ryan M, Childs, Amber-Robyn, Mann, Bruce Q, Potts, Warren M
- Authors: Foster, Ryan M , Childs, Amber-Robyn , Mann, Bruce Q , Potts, Warren M
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443128 , vital:74080 , https://doi.org/10.1080/15627020.2022.2035254
- Description: The South African spearfishery targets a variety of data-deficient species, which are consequently poorly managed. This study aimed to describe the age and growth of one of these species, the Cape knifejaw, Oplegnathus conwayi, which is endemic to the southern and eastern coasts of South Africa. Monthly biological samples were collected through research spearfishing (n = 170) and augmented by recreational spearfishers’ catches (n = 135). The results indicated that the O. conwayi population sex ratio was skewed towards males (1M:0.6F). The length- and age-frequency distributions were similar between sexes. Oplegnathus conwayi is a relatively slow-growing species, with a maximum-recorded age of 27 years. No significant differences were observed between male and female growth, with the overall population growth curve being best described as L(t) = 697.15(1 − e−0.06(t−6.30)). The slow growth observed in this species is characteristic of a species that is vulnerable to overexploitation, and accordingly a precautionary approach to future management is recommended.
- Full Text:
- Date Issued: 2022
- Authors: Foster, Ryan M , Childs, Amber-Robyn , Mann, Bruce Q , Potts, Warren M
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443128 , vital:74080 , https://doi.org/10.1080/15627020.2022.2035254
- Description: The South African spearfishery targets a variety of data-deficient species, which are consequently poorly managed. This study aimed to describe the age and growth of one of these species, the Cape knifejaw, Oplegnathus conwayi, which is endemic to the southern and eastern coasts of South Africa. Monthly biological samples were collected through research spearfishing (n = 170) and augmented by recreational spearfishers’ catches (n = 135). The results indicated that the O. conwayi population sex ratio was skewed towards males (1M:0.6F). The length- and age-frequency distributions were similar between sexes. Oplegnathus conwayi is a relatively slow-growing species, with a maximum-recorded age of 27 years. No significant differences were observed between male and female growth, with the overall population growth curve being best described as L(t) = 697.15(1 − e−0.06(t−6.30)). The slow growth observed in this species is characteristic of a species that is vulnerable to overexploitation, and accordingly a precautionary approach to future management is recommended.
- Full Text:
- Date Issued: 2022
Is the instrumental approach a ‘silver bullet’for addressing non-compliance in recreational fisheries: A South African case study
- Bova, Christopher S, Stephens, Jed, Aswani, Shankar, Potts, Warren M
- Authors: Bova, Christopher S , Stephens, Jed , Aswani, Shankar , Potts, Warren M
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/391359 , vital:68644 , xlink:href="https://doi.org/10.1016/j.fishres.2022.106439"
- Description: Non-compliance with recreational fishery regulations is considered to be one of the biggest threats to the sustainability of fisheries. Dedicated non-compliance studies are seldom carried out at the national level which makes it difficult to discern the behavioural compliance norms within a population. The instrumental approach for compliance is the traditional paradigm in recreational fisheries. It postulates that increased enforcement activities and the corresponding punishment will improve compliance behaviour, although there is little empirical evidence for such a supposition within the recreational fisheries context. Using face-to-face encounter surveys employing the ballot box method for reducing social desirability bias (SDB), South African marine shore-based fishery (MSBF) participants were questioned on their compliance behaviour with a set of regulations pertaining to the fishery. Overall non-compliance levels were very high (52%), and non-compliance levels with individual regulations varied based on provincial locality. Perceptions and observations of enforcement activity had no significant impact on compliance behaviour. Participants that had previously been caught by law enforcement violating the regulations were still more likely to violate the regulations than participants that had not faced enforcement action. Results indicate that calls for increased enforcement as a means of improving compliance behaviour are questionable in the South African MSBF, and further emphasise the need to develop alternative approaches, such as those pertaining to normative theory, within recreational fisheries.
- Full Text:
- Date Issued: 2022
- Authors: Bova, Christopher S , Stephens, Jed , Aswani, Shankar , Potts, Warren M
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/391359 , vital:68644 , xlink:href="https://doi.org/10.1016/j.fishres.2022.106439"
- Description: Non-compliance with recreational fishery regulations is considered to be one of the biggest threats to the sustainability of fisheries. Dedicated non-compliance studies are seldom carried out at the national level which makes it difficult to discern the behavioural compliance norms within a population. The instrumental approach for compliance is the traditional paradigm in recreational fisheries. It postulates that increased enforcement activities and the corresponding punishment will improve compliance behaviour, although there is little empirical evidence for such a supposition within the recreational fisheries context. Using face-to-face encounter surveys employing the ballot box method for reducing social desirability bias (SDB), South African marine shore-based fishery (MSBF) participants were questioned on their compliance behaviour with a set of regulations pertaining to the fishery. Overall non-compliance levels were very high (52%), and non-compliance levels with individual regulations varied based on provincial locality. Perceptions and observations of enforcement activity had no significant impact on compliance behaviour. Participants that had previously been caught by law enforcement violating the regulations were still more likely to violate the regulations than participants that had not faced enforcement action. Results indicate that calls for increased enforcement as a means of improving compliance behaviour are questionable in the South African MSBF, and further emphasise the need to develop alternative approaches, such as those pertaining to normative theory, within recreational fisheries.
- Full Text:
- Date Issued: 2022
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