Larvae of Pareuchaetes insulata were released in South Africa for the biological control of the invasive weed Chromolaena odorata. Pareuchaetes insulata has proved to be a difficult agent to establish in the field in South Africa, for various possible reasons. Populations collected from Florida and Jamaica (their aboriginal home) were released separately at several sites each in South Africa, but only one population (Florida) was definitely established. It is possible that adults from this established population interbred with adults from the Jamaican population released at nearby sites. The aims of this study were to determine whether there were any differences in biology between the two populations and whether hybridization affected the fitness of either. Trials involved: (i) pure-breeding of both Florida (F) and Jamaica (J) populations; (ii) cross-breeding of the two populations and; (iii) back-crossing of the hybrids with the parent populations. The fitness of these populations was determined by measuring adult longevity and fecundity, egg viability, and larval development and survival rates. The F population was superior to the J population in most of parameters measured, including fecundity. Hybridization of these populations reduced the fitness of the F population. It is unknown whether these differences in fitness reflect differences in their native regions, laboratory cultures or response to South African C. odorata. It appears that different populations of P. insulata have different levels of fitness, and that hybridization negatively affects the fitness of stronger populations. The lower fitness of the J population may have reduced its likelihood of establishing successfully, and even reduced the fitness of the established F population where the populations came into contact. These results caution that the possible consequences of mixing different genotypes of a biocontrol agent species should be properly investigated prior to their release in the same country. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

With a declining population of roughly 3000-5000 individuals in Africa, African wild dogs (Lycaon pictus) are one of the most endangered carnivores in the world. As the global human population expands, it is becoming increasingly unlikely that large portions of land will be set aside for conservation, especially in developing countries. Thus, recent wild dog conservation efforts in South Africa have concentrated on establishing a managed metapopulation. A metapopulation is a group of geographically isolated subpopulations of a species that are managed (using supplementation and harvesting) to mimic natural gene flow. The Great Fish River Nature Reserve (GFRNR) in the Eastern Cape Province of South Africa has been identified as a potential reserve to become part of the national wild dog metapopulation. My research aimed to conduct a feasibility assessment of the long-term (~ 25 years) success of a wild dog reintroduction into the GFRNR. This assessment included biological modelling of wild dogs and their expected prey, and determining the potential anthropogenic threats to wild dogs on the private and communal land surrounding the reserve. I used VORTEX population modelling and determined that the GFRNR is likely to have a wild dog carrying capacity of ~22 individuals. Using a 25-year modelling simulation, the most appropriate wild dog reintroduction scenario would be to reintroduce six females and four males initially and supplement the population with one female and two males in years 3, 10, 15 and 23. In addition, the harvesting/removal of one male and one female in years 10 and 20 would be required to ensure 100% population persistence and adequate genetic diversity. Kudu (Tragelaphus strepsiceros) and bushbuck (Tragelaphus scriptus) are expected to be the two most important prey species for reintroduced wild dogs in the GFRNR. Furthermore, wild dogs are likely to prefer the north-western and south-western sectors of the reserve because of the relatively high prey densities in these areas. However, regular monitoring of both the potential prey and the wild dog populations is essential to ensure persistence of the wild dogs and to prevent prey populations decreasing precipitously. Using structured questionnaire interviews (n = 128), I found that while neighbouring land owners and local communities were generally positive about the potential wild dog reintroduction (56 % of all respondents), several threats to wild dogs were identified along the reserve boundary and on the adjoining unprotected land. Some private landowners and members of rural communities around the reserve (34 %) stated that they would kill any wild dogs that dispersed onto their land. In addition, some respondents (8 %) admitted to believing in traditional uses for wild dog products (e.g. fur) which could result in the illegal killing of wild dogs outside of the GFRNR for traditional purposes. Poaching and the presence of unvaccinated domestic dogs on neighbouring land were also identified as being potential threats to a reintroduced wild dog population. However, such anthropogenic threats appear to be localised to the western and southern boundaries of the reserve. Therefore, by implementing preventative measures (such as anti-snare collars, anti-poaching patrols and vaccination against rabies and canine distemper) the likelihood of such threats occurring can be reduced. I conclude that the GFRNR can sustain a population of wild dogs and successfully contribute to South Africa‘s national metapopulation. An additional reserve will benefit the country‘s metapopulation by increasing the number of wild dogs available for translocation, thereby increasing genetic diversity and overall resilience (to environmental change, disease etc.) of South Africa‘s wild dog population. This will contribute towards the future conservation of this endangered species.

It was previously thought that the South African chokka squid Loligo reynaudi is exclusively an inshore, shallow water spawner. Although spawning mostly within shallow bays (<60 m) the presence of squid eggs in trawls at depths up to 130 m indicates this species frequently makes use of deeper spawning areas on the mid-shelf. The extent of mid-shelf spawning (referred to as deep spawning) and the contribution to recruitment has yet to be assessed. Studies have shown mid-shelf bottom temperature to vary considerably from those inshore, suggesting chokka squid spawn in two very different oceanographic environments. Considering these apparent environmental differences, what leads to the mid-shelf environment becoming a suitable spawning habitat? Does a suitable benthic habitat, required for the attachment of egg pods, occur on the mid-shelf? These questions are not only important for determining the extent of deep spawning, but also to the understanding of factors “driving” deep spawning. The fate of deep spawned hatchlings is another unknown. It has been proposed that the main chokka squid inshore spawning grounds are positioned to exploit the net westward currents on the Eastern Agulhas Bank, i.e. paralarvae would be transported west from the hatching site to the cold ridge, an area of high primary and secondary productivity on the Central Agulhas Bank. This concept has come to be known as the Western Transport Hypothesis. Lagrangian ROMS-IBMs (regional ocean model system – individual-based model) predict the net westward transport of paralarvae from both the inshore and deep spawning grounds, to the cold ridge. These simulations were used to investigate the transport of hatchlings to the cold ridge feeding grounds before the exhaustion of yolk reserves. The fate of paralarvae on reaching the feeding grounds has not yet been investigated. This work has contributed new knowledge to our understanding of deep spawning and its role in recruitment. Specific aims of this study were to (1) determine the extent, range and importance of the deep spawning grounds relative to those inshore; (2) investigate the deep spawning ground habitat (Agulhas Bank mid-shelf) morphology and oceanographic environment; (3) determine the transport and survival of deep spawned hatchlings; and (4) investigate the origin and distribution of chokka squid paralarvae on the Agulhas Bank. The extent, depth range and importance of the deep spawning grounds, relative to those inshore was assessed using 23 years of demersal trawl survey data. Data for both the west and south coasts of South Africa were examined for egg capsules. No spawning was found on the west coast. Data showed that chokka squid preferred the Eastern Agulhas Bank for spawning. Spawning occurred not only inshore but also on the mid-shelf extending to depths of 270 m near the shelf edge. The majority of deep spawned eggs however, were found in the depth range 71-130 m. Squid egg density markedly decreased beyond 70 m, suggesting delineation between the inshore and deep spawning grounds. Total egg biomass calculations for depths shallower and deeper than 70 m indicated the coastal area to be strongly favoured, i.e. 82 vs. 18%. These results contest the commonly accepted notion that chokka squid is an inshore spawner and redefine the spawning grounds to extend across the shelf. Apart from an initial study investigating bottom temperature on the mid-shelf, very little is known about the deep spawning habitat. St Francis Bay, a commonly used spawning location, was chosen as a demonstration area for further study. The deep spawning grounds (71-130 m) were mapped and benthic habitat described from underwater video footage. A study investigating cross-shelf bottom conditions was undertaken off Thys Bay. CTD data were used to compare seasonal bottom temperature and oxygen on the St Francis Bay inshore and deep spawning grounds. Squid movement between the two spawning habitats was assessed using filament tagging. Predation and fishing pressure across the spawning grounds was reviewed. The mid-shelf benthic habitat was found to be similar to that inshore and available for spawning. Despite the generally colder bottom temperatures on the mid-shelf, this study showed that bottom temperature in deeper waters can at times be warmer than inshore. Although mid-shelf warming events lasted from a few hours to a number of days, they resulted in similar conditions to those on the inshore spawning grounds. It is likely these events act to expand or shift spawning habitat. The movement of squid between the two spawning habitats makes it possible for them to seek patches of warm bottom water with appropiate substrate. This suggests they are spawning habitat opportunists. Predation and fishing pressure appear to be higher on the inshore spawning grounds. It is feasible that this also forces spawners to seek out more favourable habitat offshore. An individual-based model was used to predict the fate of mid-shelf and inshore hatched paralarvae. Within the model, both the highly productive cold ridge and inshore spawning grounds were considered feeding or nursery areas. Paralarvae were released from six inshore and six deep spawning sites, spanning the coast between Port Alfred and Knysna. All paralarvae not reaching the feeding areas before the exhaustion of yolk-reserves (≤5 days), not retained within the feeding grounds (≥14 days), and not retained on the Agulhas Bank after exiting the feeding grounds were considered lost. This work illustrated the dependence of paralarval transport success on both spawning location and time of hatching, as established in earlier studies. The current IBM has expanded on initial work, emphasizing the importance of the cold ridge and inshore spawning grounds as nursery areas for deep and inshore spawned paralarvae, respectively. This work has highlighted the complex interactions between processes influencing recruitment variability for chokka squid. Possible relationships between periods of highest recruitment success and spawning peaks were identified for both spawning habitats. Based on the likely autumn increase in deep spawning off Tsitsikamma, and the beneficial currents during this period, it can be concluded deep spawning may at times contribute significantly to recruitment. This is particularly true for years where the cold ridge persists into winter. Data on chokka squid paralarval distribution are scarce. Paralarval distribution and abundance, in relation to Agulhas Bank oceanography, was investigated using bongo caught paralarvae and corresponding oceanographic data. Individual-based models (IBMs) were used to predict the origin or spawning site of the wild caught paralarvae, with reference to inshore versus deep spawning. Although failing to predict realistic points of origin, this study provided evidence to support a number of scenarios previously assumed to influence chokka squid recruitment. First is the possible influence of coastal upwelling on the retention, and hence spatial distribution, of paralarvae on the inshore spawning grounds. The second factor thought to impact recruitment is the loss of paralarvae from the Agulhas Bank ecosystem. This study confirmed the removal of paralarvae from the Eastern Agulhas Bank due to Agulhas Current boundary phenomena and resultant offshelf leakage. In addition, data suggested that the formation of the cold ridge could enhance retention on the Central Agulhas Bank, and so prevent offshelf leakage from the Central and Western Agulhas Bank. A synthesis of the main conclusions is presented. Implications of the findings and directions for future research are discussed.

The re-introduction of black rhinoceros onto the Great Fish River Reserve in the Eastern Cape, following the species absence for over a century, created an opportunity to study this species in the thicket biome, and in particular the succulent thicket of the Great Fish River valley. The thicket biome is quite different from the habitats in which other extant populations of these animals are found and where studies of their demography have been undertaken. Data collection occurred from May 1986, with the arrival of the first four animals to December 2008, when the population was estimated to be 144 individuals. A variety of monitoring techniques were used including direct ground observations, aerial helicopter census, aerial monitoring by microlight aircraft, camera traps and opportunistic observations, each with its own advantages and disadvantages. The combination of methods and effort has resulted in the population being recognized as completely known with up to 97% of the animals being located at least once per year with a mean frequency of sightings of 11.5 per animal per year. In 2008, the population was about 20% juvenile, 36% sub-adult and 44% adult with a female biased sex ratio of 1.3 females per male. Mean age at first birth was about 80 months and this increased significantly with increasing density of black rhinoceroses. Mean intercalf interval was about 28 months and 41% of adult females gave birth each year. Mortality rates were low for juveniles, higher for sub-adults and higher for males than females. There was a weak but significant positive effect of density on male mortality. Population growth rate was about 10% and was not significantly affected by density. These results suggest that this population is beginning to show the first indications of density dependant constraints and that harvesting should be implemented in order to maintain the productive tempo. A secondary goal of the Management Plan will then be realized as the population functions as a donor to establish founder populations elsewhere within the Diceros bicornis minor range.