The last two remaining populations of the critically endangered estuarine pipefish are inbred and not genetically distinct
- Authors: Weiss, Sven-Erick , Emami-Khoyi, Arsalan , Kaiser, Horst , Cowley, Paul D , James, Nicola C , Jansen van Vuuren, Bettine , Whitfield, Alan K , Teske, Peter R
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/445101 , vital:74347 , https://doi.org/10.3389/fmars.2021.756595
- Description: Temporary wetland ecosystems are common in arid and semi‐arid envi-ronments, and are inhabited by diverse invertebrate communities. Little is known about the dynamics of genetic connectivity in the geograph-ically scattered populations of these wetland specialists. The current study investigated the spatial genetic structure and dispersal history of a recently described calanoid copepod, Lovenula raynerae, reported from temporary wetlands in the Eastern Cape province of South Africa. We tested whether the species represents a single, well-connected population or comprises different regional genetic groups, some of which may be rare or endangered.
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- Date Issued: 2022
High genetic diversity and limited spatial structure in an endangered, endemic South African sparid, the red steenbras Petrus rupestris:
- Authors: Gouws, Gavin , Kerwath, S E , Potts, Warren M , James, Nicola C , Vine, Niall G , Cowley, Paul D
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160379 , vital:40440 , DOI: 10.2989/1814232X.2020.1788640
- Description: The red steenbras Petrus rupestris is endemic to South Africa, occurring from False Bay in the Western Cape Province to St Lucia in the province of KwaZulu-Natal. This species, the largest member of the family Sparidae, has undergone a substantial stock decline as a result of overfishing and is considered to be collapsed. Various aspects of its life history, including high residency, predictable migrations, late maturity and longevity, have made it vulnerable to overexploitation. This study analysed the diversity and genetic structure of red steenbras across seven sampling regions, using mitochondrial (control region) and nuclear (S7 intron 1) DNA markers.
- Full Text:
- Date Issued: 2020
Implantation, orientation and validation of a commercially produced heart-rate logger for use in a perciform teleost fish:
- Authors: Muller, Cuen , Childs, Amber-Robyn , Duncan, Murray I , Skeeles, Michael R , James, Nicola C , Van der Walt, Kerry-Ann , Winkler, Alexander C , Potts, Warren M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148494 , vital:38744 , doi.org.wam.seals.ac.za/10.1093/conphys/coaa035
- Description: Quantifying how the heart rate of ectothermic organisms responds to environmental conditions (e.g. water temperature) is important information to quantify their sensitivity to environmental change. Heart rate studies have typically been conducted in lab environments where fish are confined. However, commercially available implantable heart rate biologgers provide the opportunity to study free-swimming fish. Our study aimed to determine the applicability of an implantable device, typically used on fusiform-shaped fish (e.g. salmonids), for a perciform fish where morphology and anatomy prevent ventral incisions normally used on fusiform-shaped fish.
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- Date Issued: 2020
Assessment of the likely sensitivity to climate change for the key marine species in the southern Benguela system
- Authors: Ortega-Cisneros, Kelly , Yokwana, Sibusiso , Sauer, Warwick H H , Cochrane, Kevern L , James, Nicola C , Potts, Warren M , Singh, L , Smale, Malcolm J , Wood, A , Pecl, Gretta T
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123211 , vital:35415 , https://doi.10.2989/1814232X.2018.1512526
- Description: Climate change is altering many environmental parameters of coastal waters and open oceans, leading to substantial present-day and projected changes in the distribution, abundance and phenology of marine species. Attempts to assess how each species might respond to climate change can be data-, resource- and time-intensive. Moreover, in many regions of the world, including South Africa, species may be of vital socioeconomic or ecological importance though critical gaps may exist in our basic biological or ecological knowledge of the species. Here, we adapt and apply a trait-based sensitivity assessment for the key marine species in the southern Benguela system to estimate their potential relative sensitivity to the impacts of climate change. For our analysis, 40 priority species were selected based on their socioeconomic, ecological and/or recreational importance in the system. An extensive literature review and consultation with experts was undertaken concerning each species to gather information on their life history, habitat use and potential stressors. Fourteen attributes were used to estimate the selected species’ sensitivity and capacity to respond to climate change. A score ranging from low to high sensitivity was given for each attribute, based on the available information. Similarly, a score was assigned to the type and quality of information used to score each particular attribute, allowing an assessment of data-quality inputs for each species. The analysis identified the white steenbras Lithognathus lithognathus, soupfin shark Galeorhinus galeus, St Joseph Callorhinchus capensis and abalone Haliotis midae as potentially the most sensitive species to climate-change impacts in the southern Benguela system. There were data gaps for larval dispersal and settlement and metamorphosis cues for most of the evaluated species. Our results can be used by resource managers to determine the type of monitoring, intervention and planning that may be required to best respond to climate change, given the limited resources and significant knowledge gaps in many cases.
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- Date Issued: 2018
Metabolic activity throughout early development of dusky kob Argyrosomus japonicus (Sciaenidae)
- Authors: Edworthy, Carla , James, Nicola C , Erasmus, B , Kemp, Justin O G , Kaiser, Horst , Potts, Warren M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125159 , vital:35737 , https://doi.10.2989/1814232x.2018.1441907
- Description: Metabolism quantifies the energy-consuming activities of an organism (Nelson 2016) and is used as an indication of how organisms partition energy resources to activities that allow them to survive, grow and reproduce (Post and Lee 1996). The metabolic profile, which is a composition of the various metabolic rates of an individual, therefore gives an indication of the efficiency of energy transformation and allocation (Fry 1971; Brown et al. 2004). McKenzie et al. (2016) suggested that an organism’s physiology contributes towards its ability to survive under specific environmental conditions. As a result, physiological condition can be a reflection of the performance and fitness of an organism (Pörtner 2010). When combined with information on changing environmental conditions, physiological information can provide insight into species- and community-level responses (Pörtner and Farrell 2008). These kinds of data have served numerous ecological applications, including resource management, conservation (McKenzie et al. 2016) and climate-change assessments (Pörtner and Farrell 2008).
- Full Text:
- Date Issued: 2018
Life-histories explain the conservation status of two estuary-associated pipefishes
- Authors: Whitfield, Alan K , Mkare, Thomas K , Teske, Peter R , James, Nicola C , Cowley, Paul D
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/445087 , vital:74346 , https://doi.org/10.1016/j.biocon.2017.06.024
- Description: Two endemic southern African pipefish species (Teleostei: Syngnathidae) co-occur in estuaries on the southeast coast of South Africa. The larger longsnout pipefish, Syngnathus temminckii, is abundant and has a wide range that comprises coastal and estuarine habitats in all three of the region's marine biogeographic provinces. In contrast, the smaller estuarine pipefish S. watermeyeri is critically endangered, and confined to a few warm-temperate estuaries. Here, we explore reasons for these considerable differences in conservation status.
- Full Text:
- Date Issued: 2017
Age and growth of Cape stumpnose Rhabdosargus holubi (Pisces: Sparidae) in the Eastern Cape, South Africa
- Authors: Farthing, Matthew William , James, Nicola C , Potts, Warren M
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/122891 , vital:35365 , https://doi.org/10.2989/1814232X.2016.1156577
- Description: Rhabdosargus holubi (Steindachner, 1881) is a small (maximum size = 450 mm total length; Heemstra and Heemstra 2004) sparid that is distributed along the south-east coast of Africa from St Helena Bay, South Africa, to Maputo, Mozambique (Götz and Cowley 2013). Spawning occurs in the nearshore marine environment primarily during winter, specifically May–August in KwaZulu-Natal (KZN) (Wallace 1975) and July–February in the South-Eastern Cape (Whitfield 1998). Individuals reach 50% sexual maturity at approximately 150 mm standard length (SL) in the Eastern Cape (Whitfield 1998). The early life stages are transported by the south-westward-flowing Agulhas Current, and recruit as post-flexion larvae and early juveniles into estuaries during late winter and early summer (Blaber 1974). The warm temperatures and high nutrient levels in estuaries favour fast growth (Blaber 1973a), and fish spend their first year of life in these environments, migrating back out to sea after reaching approximately 120 mm SL. Some individuals remain trapped in closed estuaries, where they may reach sizes greater than 200 mm SL (James et al. 2007a). Rhabdosargus holubi is the dominant estuarine-dependent marine teleost species recorded in permanently open and temporarily open/closed estuaries in the warm-temperate region, which spans the south, south-east and east coast of South Africa (Harrison 2005). The species is also an important component of the linefishery in many SouthAfrican estuaries (10–15.6% by number) (Pradervand and Baird 2002), particularly in Eastern Cape estuaries (Cowley et al. 2003). These figures underestimate the presence of R. holubi, as most individuals making use of estuaries are young, feeding predominately on filamentous macroalgae and diatom flora, and are generally too small to be caught with hook and line (De Wet and Marais 1990). James et al. (2007b) showed that R. holubi made up 34–92% of the annual seine-net catch in the East Kleinemonde Estuary. Rhabdosargus holubi is also important in the KZN shorebased linefishery, representing 4.6% of the total landed catch (Dunlop and Mann 2012).
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- Date Issued: 2016
Population dynamics and biology of an invasive population of mosquitofish Gambusia affinis in a temperate estuarine lake system
- Authors: Sloterdijk, Hans , James, Nicola C , Smith, M Kyle S , Ekau, Werner , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443919 , vital:74171 , https://doi.org/10.1080/15627020.2015.1021169
- Description: This study investigates the distribution, relative abundance, population growth and biology of the alien invasive fish Gambusia affinis in the Wilderness Lakes System, a coastal lake system in the warm-temperate region of South Africa. Fish were collected throughout the system during four seasonal sampling trips in spring (October 2010), summer (February 2011), autumn (May 2011) and winter (July 2011). Gambusia affinis were widespread and abundant in all habitats from the freshwater reaches of the inflowing Touw River to the more saline lakes and estuary. Sex ratio was generally female dominated and mean length at maturity was 14.7 mm standard length (SL) for males and 20.3 mm SL for females. Reproduction was strongly seasonal with reproductively active fish sampled in spring and summer but not in autumn and winter. Relative abundance also varied seasonally, with populations following typical ‘boom and bust’ population dynamics. By winter, the population in all habitats was lower with mortality rates as high as 85%. The stronghold of the population appears to be in the channels between the lakes, where relative abundance was more consistent and winter mortality rates were lower. The survivors, which are primarily females, then reconstitute the population in the spring and summer months.
- Full Text:
- Date Issued: 2015
Review of the projected impacts of climate change on coastal fishes in southern Africa
- Authors: Potts, Warren M , Götz, Albrecht , James, Nicola C
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125899 , vital:35830 , https://doi.10.1007/s11160-015-9399-5
- Description: The coastal zone represents one of the most economically and ecologically important ecosystems on the planet, none more so than in southern Africa. This manuscript examines the potential impacts of climate change on the coastal fishes in southern Africa and provides some of the first information for the Southern Hemisphere, outside of Australasia. It begins by describing the coastal zone in terms of its physical characteristics, climate, fish biodiversity and fisheries. The region is divided into seven biogeographical zones based on previous descriptions and interpretations by the authors. A global review of the impacts of climate change on coastal zones is then applied to make qualitative predictions on the likely impacts of climate change on migratory, resident, estuarine-dependent and catadromous fishes in each of these biogeographical zones. In many respects the southern African region represents a microcosm of climate change variability and of coastal habitats. Based on the broad range of climate change impacts and life history styles of coastal fishes, the predicted impacts on fishes will be diverse. If anything, this review reveals our lack of fundamental knowledge in this field, in particular in southern Africa. Several research priorities, including the need for process-based fundamental research programs are highlighted.
- Full Text:
- Date Issued: 2015
A preliminary survey of the estuaries on the south coast of South Africa, Robberg Peninsula - Cape St Francis, with particular reference to the fish fauna : ecological overview article
- Authors: James, Nicola C , Harrison, T D
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:7144 , http://hdl.handle.net/10962/d1011842
- Description: A basic ichthyofaunal and physico-chemical survey of the coastal outlets on the south coast of South Africa (Robberg Peninsula to Cape St Francis) was undertaken during November 1994 and September 1995. Some 27 systems were identified along this stretch of coast and of these, 48% (Brak, Helpmekaars, Klip, Witels, Geelhoutbos, Kleinbos, Bruglaagte, Langbos, Sanddrif, Eerste, Boskloof, Kaapsedrif and Klipdrif [Wes]) comprised the inlets of coastal streams that offer little habitat for fishes, 26% (Sout, Bloukrans, Lottering, Elandsbos, Storms, Elands and Groot [Oos]) are located within deeply incised valleys within the Tsitsikamma region and provide limited littoral habitat for estuary-associated fishes; 26% of the systems (Piesang, Keurbooms, Matjies, Groot [Wes], Tsitsikamma, Klipdrif [Oos], Slang) appear to serve some estuarine function for both marine migrant and resident species although some of these may also be limited due to their small size and infrequent connection with the sea. This study serves to emphasize the ecological importance of these latter estuaries within this coastal sector.
- Full Text:
- Date Issued: 2009
A preliminary survey of the estuaries on the south coast of South Africa, Cape St Blaize, Mossel Bay - Robberg Peninsula, Plettenberg Bay, with particular reference to the fish fauna
- Authors: James, Nicola C , Harrison, T D
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:7141 , http://hdl.handle.net/10962/d1011834
- Description: The coastal river systems on the south coast of South Africa from Cape St Blaize to Robberg Peninsula were surveyed during October and November 1994. The ichthyofaunal and physico-chemical characteristics of each system are presented and their suitability as estuarine nursery areas is discussed. Five systems (Rooi, Meul, Grooteiland, Kranshoek and Crooks) are outlets of small coastal streams and probably provide little or no habitat for either resident estuarine or migrant marine fishes owing to their small size. Four systems (Maalgate, Gwaing, Skaapkop and Kaaimans) are located within deeply incised valleys and have a permanent connection with the sea. The amount of marginal and intertidal habitat available to fishes, however, is limited due to their morphology. Six systems (Hartenbos, Groot Brak, Touw, Swartvlei, Goukamma and Noetsie) are intermittently open to the sea. Although the Touw and Swartvlei are connected to coastal lake systems, flow within these estuaries is not sufficient to prevent the build up of a sand barrier at the mouth. The Hartenbos, Groot Brak, Goukamma, and Noetsie are also periodically closed by a sand bar. The construction of a dam in the lower catchment of the Groot Brak has affected the hydrology of the system. The two remaining estuaries (Klein Brak and Knysna) are permanently open. In addition to strong tidal currents, the fixing of the mouth of the Knysna Estuary between rocky headlands also serves to maintain a permanent connection with the sea. Mugilidae and Sparidae were represented by the greatest number of species, and also dominated catches numerically and by mass. The fish fauna of all the estuaries surveyed were dominated by the juveniles of estuarine-dependent marine species and estuarine-resident species were also well represented in catches. The estuaries surveyed provide a vital habitat for both marine migrant species and resident species, most of which are endemic to the region.
- Full Text:
- Date Issued: 2008