A description of gametogenesis in the panga Pterogymnus laniarius (Pisces: Sparidae) with comments on changes in maturity patterns over the past two decades
- Booth, Anthony J, Hecht, Thomas
- Authors: Booth, Anthony J , Hecht, Thomas
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123542 , vital:35452 , https://doi.org/10.1080/02541858.1997.11448428
- Description: A description of gametogenesis in the panga Pferogymnus laniarius, a common endemic seabream species inhabiting the Agulhas Bank, South Africa, is presented. After sexual maturity, oogenesis and spermatogenesis continued throughout the year and were found to be similar to these processes in other seabream species and teleosts in general. Analysis of maturity data over the past two decades revealed a significant change in both age and size-at-maturity, a response to fishing pressure.
- Full Text:
- Date Issued: 2015
- Authors: Booth, Anthony J , Hecht, Thomas
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123542 , vital:35452 , https://doi.org/10.1080/02541858.1997.11448428
- Description: A description of gametogenesis in the panga Pferogymnus laniarius, a common endemic seabream species inhabiting the Agulhas Bank, South Africa, is presented. After sexual maturity, oogenesis and spermatogenesis continued throughout the year and were found to be similar to these processes in other seabream species and teleosts in general. Analysis of maturity data over the past two decades revealed a significant change in both age and size-at-maturity, a response to fishing pressure.
- Full Text:
- Date Issued: 2015
Life-history characteristics of an age-validated established invasive African sharptooth catfish, Clarias gariepinus, population in a warm-temperate African impoundment
- Wartenberg, Reece, Weyl, Olaf L F, Booth, Anthony J, Winker, Henning
- Authors: Wartenberg, Reece , Weyl, Olaf L F , Booth, Anthony J , Winker, Henning
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443542 , vital:74130 , https://hdl.handle.net/10520/EJC145790
- Description: It has been suggested that the invasive, omnivorous Clarias garipienus is capable of rapid invasions and long-term persistence in recently inhabited freshwater systems. To test this hypothesis, the life history of the established, extralimital Darlington Dam (33°10'31"S, 25°09'13"E) population was investigated. By counting post-fluorescent mark increments on otoliths from 21 chemically tagged wild fish recaptured 244-537 days later, the deposition of growth zones, comprising alternating opaque and translucent bands, was validated as annual. Examination of sectioned otoliths from 175 fish revealed that the oldest fish, two males of 840 and 1074 mm total length (TL), were 25 years old - 10 years older than previously described for any C. gariepinus population. The oldest female was 885 mm TL and 21 years old. Length-at-age was subsequently described using the von Bertalanffy growth model. Combined-sex growth was best described as Lt = 931.7 ( 1 - exp(-0.15(t +2.43))) mm TL. Total mortality (Z) was calculated using catch curve analysis and the Chapman and Robson estimator to be 0.35/yr. The presence of specimens 15 years and older indicates that these fish established quickly and supports the finding that mortality rates are low, which, in turn, suggests likely long-term population persistence.
- Full Text:
- Date Issued: 2014
- Authors: Wartenberg, Reece , Weyl, Olaf L F , Booth, Anthony J , Winker, Henning
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443542 , vital:74130 , https://hdl.handle.net/10520/EJC145790
- Description: It has been suggested that the invasive, omnivorous Clarias garipienus is capable of rapid invasions and long-term persistence in recently inhabited freshwater systems. To test this hypothesis, the life history of the established, extralimital Darlington Dam (33°10'31"S, 25°09'13"E) population was investigated. By counting post-fluorescent mark increments on otoliths from 21 chemically tagged wild fish recaptured 244-537 days later, the deposition of growth zones, comprising alternating opaque and translucent bands, was validated as annual. Examination of sectioned otoliths from 175 fish revealed that the oldest fish, two males of 840 and 1074 mm total length (TL), were 25 years old - 10 years older than previously described for any C. gariepinus population. The oldest female was 885 mm TL and 21 years old. Length-at-age was subsequently described using the von Bertalanffy growth model. Combined-sex growth was best described as Lt = 931.7 ( 1 - exp(-0.15(t +2.43))) mm TL. Total mortality (Z) was calculated using catch curve analysis and the Chapman and Robson estimator to be 0.35/yr. The presence of specimens 15 years and older indicates that these fish established quickly and supports the finding that mortality rates are low, which, in turn, suggests likely long-term population persistence.
- Full Text:
- Date Issued: 2014
Computer-aided identification of coelacanths, latimeria chalumnae, using scale patterns
- Thornycroft, Rosanne E, Booth, Anthony J
- Authors: Thornycroft, Rosanne E , Booth, Anthony J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124013 , vital:35526 , https://doi.10.1080/17451000.2011.628679
- Description: Despite coelacanths, Latimeria chalumnae, being listed as either endangered by CITES or critically endangered by the IUCN, their population size within South Africa is unknown and still needs to be estimated. Their conservation status unfortunately excludes the use of conventional tagging to mark individual animals for a possible mark-recapture experiment. This study shows that because coelacanths have a unique spot patterning it is possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator, the software accurately identified between 56 and 92% of the individuals. Indentification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60˚ could be accurately identified in photographs, although the percentage of fish correctly identified without operator-intervention decreased rapidly with increasing yaw angle. Computer-aided identification should therefore facilitate future coelacanth research as it is both efficient and accurate while also reducing potential stress on the animals observed.
- Full Text:
- Date Issued: 2012
- Authors: Thornycroft, Rosanne E , Booth, Anthony J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124013 , vital:35526 , https://doi.10.1080/17451000.2011.628679
- Description: Despite coelacanths, Latimeria chalumnae, being listed as either endangered by CITES or critically endangered by the IUCN, their population size within South Africa is unknown and still needs to be estimated. Their conservation status unfortunately excludes the use of conventional tagging to mark individual animals for a possible mark-recapture experiment. This study shows that because coelacanths have a unique spot patterning it is possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator, the software accurately identified between 56 and 92% of the individuals. Indentification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60˚ could be accurately identified in photographs, although the percentage of fish correctly identified without operator-intervention decreased rapidly with increasing yaw angle. Computer-aided identification should therefore facilitate future coelacanth research as it is both efficient and accurate while also reducing potential stress on the animals observed.
- Full Text:
- Date Issued: 2012
Spatial and seasonal distribution patterns of juvenile and adult raggedtooth sharks (Carcharias taurus) tagged off the east coast of South Africa
- Dicken, Matthew L, Booth, Anthony J, Smale, Malcolm J, Cliff, G
- Authors: Dicken, Matthew L , Booth, Anthony J , Smale, Malcolm J , Cliff, G
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126997 , vital:35942 , https://doi.10.1071/MF06018
- Description: Crucial to effective fisheries management is a thorough understanding of the stock structure of a population. Understanding the spatial and seasonal distribution patterns of a species is necessary to define habitat use and evaluate the potential effects of exploitation and anthropogenic activities. This is particularly important for a species such as the raggedtooth shark (Carcharias Taurus Rafinesque, 1810), whose life-history characteristics make it particularly susceptible to over-exploitation (Pollard et al. 1996; Smith et al. 1998; Compagno 2001). Exploitation, even at low levels for a slow-growing, late-maturing species that only produces two pups every other year, could reduce the population growth rate, could reduce the population growth rate to values of λ<1.0, resulting in severe population declines in a very short time period (Baum et al. 2003).
- Full Text:
- Date Issued: 2007
- Authors: Dicken, Matthew L , Booth, Anthony J , Smale, Malcolm J , Cliff, G
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126997 , vital:35942 , https://doi.10.1071/MF06018
- Description: Crucial to effective fisheries management is a thorough understanding of the stock structure of a population. Understanding the spatial and seasonal distribution patterns of a species is necessary to define habitat use and evaluate the potential effects of exploitation and anthropogenic activities. This is particularly important for a species such as the raggedtooth shark (Carcharias Taurus Rafinesque, 1810), whose life-history characteristics make it particularly susceptible to over-exploitation (Pollard et al. 1996; Smith et al. 1998; Compagno 2001). Exploitation, even at low levels for a slow-growing, late-maturing species that only produces two pups every other year, could reduce the population growth rate, could reduce the population growth rate to values of λ<1.0, resulting in severe population declines in a very short time period (Baum et al. 2003).
- Full Text:
- Date Issued: 2007
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