Factors affecting recapture rates of raggedtooth sharks Carcharias taurus tagged off the east coast of South Africa
- Dicken, Matthew L, Booth, Anthony J, Smale, Malcolm J
- Authors: Dicken, Matthew L , Booth, Anthony J , Smale, Malcolm J
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124493 , vital:35618 , https://doi.10.2989/AJMS.2009.31.3.9.997
- Description: Understanding differences in the recapture rate between different tags (A-, B- and C-types), capture methods (rock-and-surf anglers, scientific divers and Natal Sharks Board protection nets) and life-history stages (juvenile and adult) is critical in evaluating the results obtained from cooperative tagging programmes (CTPs). A generalised linear modelling approach, using a log-linear model, was used to determine significant differences in the probability of recapture between these various factors using data from the Oceanographic Research Institute and Port Elizabeth Museum CTPs. Between 1984 and 2004, a total of 3 385 raggedtooth sharks Carcharias taurus was tagged by volunteers from both programmes along the east coast of South Africa. A likelihood ratio test indicated significant differences in the probability of recapture between A- and C-type and B- and C-type tags (p < 0.01), between different capture methods (p < 0.05) and between juvenile and adult sharks (p < 0.01). A comparison of recapture rates between members of the CTPs also indicated a marked variability in the performance of individual taggers. The study highlights important data-quality issues inherent in large CTPs.
- Full Text:
- Date Issued: 2010
- Authors: Dicken, Matthew L , Booth, Anthony J , Smale, Malcolm J
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124493 , vital:35618 , https://doi.10.2989/AJMS.2009.31.3.9.997
- Description: Understanding differences in the recapture rate between different tags (A-, B- and C-types), capture methods (rock-and-surf anglers, scientific divers and Natal Sharks Board protection nets) and life-history stages (juvenile and adult) is critical in evaluating the results obtained from cooperative tagging programmes (CTPs). A generalised linear modelling approach, using a log-linear model, was used to determine significant differences in the probability of recapture between these various factors using data from the Oceanographic Research Institute and Port Elizabeth Museum CTPs. Between 1984 and 2004, a total of 3 385 raggedtooth sharks Carcharias taurus was tagged by volunteers from both programmes along the east coast of South Africa. A likelihood ratio test indicated significant differences in the probability of recapture between A- and C-type and B- and C-type tags (p < 0.01), between different capture methods (p < 0.05) and between juvenile and adult sharks (p < 0.01). A comparison of recapture rates between members of the CTPs also indicated a marked variability in the performance of individual taggers. The study highlights important data-quality issues inherent in large CTPs.
- Full Text:
- Date Issued: 2010
Growth and longevity of Exosphaeroma hylocoetes (Isopoda) under varying conditions of salinity and temperature
- Henninger, Tony O, Froneman, P William, Booth, Anthony J, Hodgson, Alan N
- Authors: Henninger, Tony O , Froneman, P William , Booth, Anthony J , Hodgson, Alan N
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124571 , vital:35630 , https://doi.org/10.3377/004.045.0118
- Description: Numerous studies have documented the importance of both temperature and salinity in influencing aquatic crustacean metabolic processes such as respiration and growth. For example, increased water temperatures have been shown to increase respiration rates in various species of shrimp (Chen & Nan 1993; Spanonopoulos-Hernándeza et al. 2005; Allan et al. 2006), and copepods (Isla & Perissinotto 2004). The response of invertebrates to changes in salinity is more complex, largely reflecting their evolutionary origins (Kinne 1966). For example, juvenile blue swimming crabs, Portunus pelagicus, displayed significantly faster growth and higher survival in response to increasingsalinity (Romano & Zeng 2006). Additional factors that may influence the growth rates of crustaceans include photoperiod (Gambardella et al. 1997), food availability (Shuster & Guthrie 1999) and sex (Newman et al. 2007).
- Full Text:
- Date Issued: 2010
- Authors: Henninger, Tony O , Froneman, P William , Booth, Anthony J , Hodgson, Alan N
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124571 , vital:35630 , https://doi.org/10.3377/004.045.0118
- Description: Numerous studies have documented the importance of both temperature and salinity in influencing aquatic crustacean metabolic processes such as respiration and growth. For example, increased water temperatures have been shown to increase respiration rates in various species of shrimp (Chen & Nan 1993; Spanonopoulos-Hernándeza et al. 2005; Allan et al. 2006), and copepods (Isla & Perissinotto 2004). The response of invertebrates to changes in salinity is more complex, largely reflecting their evolutionary origins (Kinne 1966). For example, juvenile blue swimming crabs, Portunus pelagicus, displayed significantly faster growth and higher survival in response to increasingsalinity (Romano & Zeng 2006). Additional factors that may influence the growth rates of crustaceans include photoperiod (Gambardella et al. 1997), food availability (Shuster & Guthrie 1999) and sex (Newman et al. 2007).
- Full Text:
- Date Issued: 2010
Establishment of translocated populations of smallmouth yellowfish, Labeobarbus aeneus (Pisces: Cyprinidae), in lentic and lotic habitats in the Great Fish River system, South Africa
- Weyl, Olaf L F, Stadtlander, Timo, Booth, Anthony J
- Authors: Weyl, Olaf L F , Stadtlander, Timo , Booth, Anthony J
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124418 , vital:35607 , https://doi.org/10.3377/004.044.0109
- Description: As a result of numerous introductions and translocations of fishes, South Africa has recently been identified as a fish invasion hotspot (Leprieur et al. 2008). In freshwater ecosystems invasion by alien species is considered a leading mechanism driving environmental change (Clavero & Garcia- Berthou 2005; Garcia-Berthou et al. 2005). In South Africa, documented effects of fish invasions include the extirpation of indigenous fishes through predation (Cambray 2003), changes in invertebrate community structure (Lowe et al. 2008) and hybridization (Canonico et al. 2005). As a result, the management of alien species is a high national priority (National Environmental Management: Biodiversity Act 2004). Such management requires an understanding of the biology, ecology and establishment success of fishes outside their native range.
- Full Text:
- Date Issued: 2009
- Authors: Weyl, Olaf L F , Stadtlander, Timo , Booth, Anthony J
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124418 , vital:35607 , https://doi.org/10.3377/004.044.0109
- Description: As a result of numerous introductions and translocations of fishes, South Africa has recently been identified as a fish invasion hotspot (Leprieur et al. 2008). In freshwater ecosystems invasion by alien species is considered a leading mechanism driving environmental change (Clavero & Garcia- Berthou 2005; Garcia-Berthou et al. 2005). In South Africa, documented effects of fish invasions include the extirpation of indigenous fishes through predation (Cambray 2003), changes in invertebrate community structure (Lowe et al. 2008) and hybridization (Canonico et al. 2005). As a result, the management of alien species is a high national priority (National Environmental Management: Biodiversity Act 2004). Such management requires an understanding of the biology, ecology and establishment success of fishes outside their native range.
- Full Text:
- Date Issued: 2009
Rapid biological assessment of the fishery potential of Xonxa Dam, near Queenstown, South Africa
- Richardson, T J, Booth, Anthony J, Weyl, Olaf L F
- Authors: Richardson, T J , Booth, Anthony J , Weyl, Olaf L F
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125798 , vital:35818 , https://doi.10.2989/AJAS.2009.34.1.9.734
- Description: In Africa, the harvesting of fish from small reservoirs has been identified as an important food resource for small rural communities, particularly those living close to waterbodies (Kapetsky and Petr 1984, Marshall and Maes 1994, van der Knaap 1994). Development of fisheries to utilize these resources has recently been identified by the African Union as a priority investment area for poverty alleviation and regional economic development (NEPAD 2005). Within a South African context, it is suspected that there will be increased interest in developing these fisheries to address major national policy objectives, which include food security, economic empowerment, optimal economic benefit from water, and poverty eradication (RSA 1998a, 1998b). South Africa, however, presents a somewhat anomalous situation. The lack of a fishing history in communities, the lack of species with a high fisheries potential, inadequate inland fisheries policy and a lack of directed fisheries development have resulted in low utilisation levels of fish resources in South African reservoirs (Weyl et al. 2007).
- Full Text:
- Date Issued: 2009
- Authors: Richardson, T J , Booth, Anthony J , Weyl, Olaf L F
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125798 , vital:35818 , https://doi.10.2989/AJAS.2009.34.1.9.734
- Description: In Africa, the harvesting of fish from small reservoirs has been identified as an important food resource for small rural communities, particularly those living close to waterbodies (Kapetsky and Petr 1984, Marshall and Maes 1994, van der Knaap 1994). Development of fisheries to utilize these resources has recently been identified by the African Union as a priority investment area for poverty alleviation and regional economic development (NEPAD 2005). Within a South African context, it is suspected that there will be increased interest in developing these fisheries to address major national policy objectives, which include food security, economic empowerment, optimal economic benefit from water, and poverty eradication (RSA 1998a, 1998b). South Africa, however, presents a somewhat anomalous situation. The lack of a fishing history in communities, the lack of species with a high fisheries potential, inadequate inland fisheries policy and a lack of directed fisheries development have resulted in low utilisation levels of fish resources in South African reservoirs (Weyl et al. 2007).
- Full Text:
- Date Issued: 2009
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