Abstract
A maximum likelihood model is developed, using mark-recapture data, to estimate total and fishing mortality rates for the dusky shark Carcharhinus obscurus in South Africa. The model accounts for tag-shedding, nonreporting of recaptured tags, the multiple release and single recapture nature of the study and the usage of two different types of tags (sheep-ear and ORI tags). Tag shedding was quantified as tags washed up on beaches and fouling of tags in protective shark nets, which amounted to 17% of all tags recovered between 1986 and 1993. The ORI tag had a higher tag-shedding rate than the sheep-ear tag. Assuming a 75% reporting rate for recaptured dusky sharks, an instantaneous fishing mortality rate was estimated to be 0.27·year-1, with a 95% confidence level ranging between 0.19 and 0.44·year-1.
| Original language | English |
|---|---|
| Pages (from-to) | 11-18 |
| Number of pages | 8 |
| Journal | South African Journal of Marine Science |
| Issue number | 18 |
| Publication status | Published - 1997 |
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ASJC Scopus subject areas
- Aquatic Science
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Mortality estimates for juvenile dusky sharks Carcharhinus obscurus in South Africa using mark-recapture data. / Govender, A.; Birnie, S. L.
In: South African Journal of Marine Science, No. 18, 1997, p. 11-18.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Mortality estimates for juvenile dusky sharks Carcharhinus obscurus in South Africa using mark-recapture data
AU - Govender, A.
AU - Birnie, S. L.
PY - 1997
Y1 - 1997
N2 - A maximum likelihood model is developed, using mark-recapture data, to estimate total and fishing mortality rates for the dusky shark Carcharhinus obscurus in South Africa. The model accounts for tag-shedding, nonreporting of recaptured tags, the multiple release and single recapture nature of the study and the usage of two different types of tags (sheep-ear and ORI tags). Tag shedding was quantified as tags washed up on beaches and fouling of tags in protective shark nets, which amounted to 17% of all tags recovered between 1986 and 1993. The ORI tag had a higher tag-shedding rate than the sheep-ear tag. Assuming a 75% reporting rate for recaptured dusky sharks, an instantaneous fishing mortality rate was estimated to be 0.27·year-1, with a 95% confidence level ranging between 0.19 and 0.44·year-1.
AB - A maximum likelihood model is developed, using mark-recapture data, to estimate total and fishing mortality rates for the dusky shark Carcharhinus obscurus in South Africa. The model accounts for tag-shedding, nonreporting of recaptured tags, the multiple release and single recapture nature of the study and the usage of two different types of tags (sheep-ear and ORI tags). Tag shedding was quantified as tags washed up on beaches and fouling of tags in protective shark nets, which amounted to 17% of all tags recovered between 1986 and 1993. The ORI tag had a higher tag-shedding rate than the sheep-ear tag. Assuming a 75% reporting rate for recaptured dusky sharks, an instantaneous fishing mortality rate was estimated to be 0.27·year-1, with a 95% confidence level ranging between 0.19 and 0.44·year-1.
UR - http://www.scopus.com/inward/record.url?scp=0031372498&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031372498&partnerID=8YFLogxK
M3 - Article
SP - 11
EP - 18
JO - African Journal of Marine Science
JF - African Journal of Marine Science
SN - 1814-232X
IS - 18
ER -