Whh Sauer

A survey of the South African shore-angling fishery

Roving creel surveys and aerial surveys of shore-angling were undertaken as part of a national investigation into linefishing in South Africa. Shore patrols utilized a random stratified sampling procedure to collect catch-and-effort data, and a questionnaire provided information on fishing effort, angler demographics, economics and attitudes towards current regulations. A total of 1 677 patrols, covering 19 616 km, was conducted between April 1994 and February 1996, during which period 9 523 anglers had their catches checked and 4 490 were interviewed. A further 16 497 km were covered by aerial surveys, when 22 609 anglers were counted. From the aerial surveys, angler densities were highest on the KwaZulu-Natal coast (4.65 anglers·km−1), followed by the Southern Cape coast (2.29 anglers·km−1), the Eastern Cape coast (0.36 anglers·km−1) and the West Coast (0.12 anglers·km−1). Catch rates varied from 1.5 kg·angler−1·day−1 on the Southern Cape coast to 0.45 kg·angler−1·day−1 on the KwaZulu-Natal coast. Total...

Movement pattern and home range of Roman Chrysoblephus laticeps

The movement behaviour of adult Roman Chrysoblephus laticeps (Sparidae) was investigated using mark-and-recapture techniques in the Goukamma Marine Protected Area (GMPA) and the Tsitsikamma National Park (TNP) on the South African temperate south coast. The study was designed to improve the spatial resolution of previous studies on Roman that suggested residence behaviour, but which could not estimate home range size. A combination of conventional barbed dart tags and visible implant fluorescent elastomer (VIFE) tags were used to tag Roman from a skiboat in the GMPA. Roman were tagged with dart tags from the shore in the TNP. Of the recaptures, 61% were within 50m of the tagging position, confirming that Roman are very resident. A few fish, independent of size and sex, moved distances up to 4km. A model was developed to quantify the degree of residence, by accounting for tag loss, mortality and the distribution of recovery effort. The probability of a Roman remaining within an area of 1ha is 0.91 (GMPA) and 0.94 (TNP) — such a small home range suggesting that individual Roman would benefit from small MPAs.

EVALUATION OF PARTICIPATION IN AND MANAGEMENT OF THE TRANSKEI SHORE LINEFISHERY

Both roving creel and aerial surveys were used to quantify fishing effort along the former Transkei coast. A stratified random sampling procedure was used during shore patrols to assess catch and effort, and a questionnaire survey provided information on total fishing effort, fisher demographics and attitudes towards current regulations. A total of 13 field trips was undertaken, during which 341 fishers were interviewed and the catches of 760 fishers examined. In all, 175 patrols were undertaken, covering in all 1 117 km. Some 24 random aerial counts of shore-fishers were also carried out during the study. From the aerial surveys, average fisher density along the Transkei coast was estimated at 0.79 fishers km−1, with an estimated total fishing effort of 170 457 fisher-days year−1. Fisher densities were highest in spring (0.9 fishers km−1) and lowest during summer (0.5 fishers km−1). Fishers were most successful in winter (1.0 fish fisher−1 inspection−1) and least successful in summer (0.4 fish fisher−1 inspection−1). Catch rates amounted to 1.4 fish fisher−1 day−1, or 0.86 kg fisher−1 day−1, and the total catch was estimated at 147 tons year−1. The main target species were bronze bream Pachymetopon grande (22%), blacktail Diplodus sargus capensis (19%) and dusky kob Argyrosomus japonicus (18%). Numerically, the most important species in the catches were elf Pomatomus saltatrix (18%) and blacktail (16%). By mass, the most important species were bronze bream (26%) and dusky kob (18%). Knowledge and compliance of regulations currently governing the linefishery in the Transkei was exceptionally poor, although most fishers supported the principle of regulations. Better-enforced and larger marine protected areas, establishment of a fisher awareness programme and improved enforcement of fishing regulations are suggestions for improving the current management of the Transkei shore-fishery.

Evidence of deep genetic divergence between populations of an important recreational fishery species, Lichia amia L. 1758, around southern Africa

Lichia amia is an important coastal recreational fishery species with a cosmopolitan distribution in the eastern Atlantic. In southern Africa, it is distributed from southern Angola to northern KwaZulu-Natal in South Africa. A recent biological survey revealed differences between Angolan and South African individuals suggesting that they may represent separate stocks. As fishery management decisions should be based on accurate knowledge of population structure, an initial survey of the genetic substructuring of L. amia was conducted on samples collected in southern Angola and South Africa. Assessment of genetic diversity and population structure was conducted using a fragment of the mitochondrial Control Region. Obtained genetic diversity levels were within the expected range for marine teleosts (h = 0.867, π = 0.007), and two deeply divergent (southern Angolan and South African) populations were identified (average φ ST = 0.78) across the Benguela Current system. These results suggest that Angolan and South African L. amia should be managed as two independent stocks. This work represents the first assessment of population genetic substructuring across the Benguela Current of a valuable coastal fishery resource, and has application for future fisheries management.

Optimisation of underwater visual census and controlled angling methods for monitoring subtidal temperate reef fish communities

Standardised sampling protocols for monitoring fish stocks are essential to assess changes in stock status and provide a means to evaluate the effectiveness of fisheries management measures, such as marine protected areas (MPAs). This study aimed to optimise two standard sampling methods, namely underwater visual census (UVC) and controlled angling, for assessing subtidal reef fish communities. In terms of efficiency, variability and bias, UVC transects were found to be superior to point counts. For controlled angling, an effort of two angler-hours per fishing station provided low catch variability, high catch per unit effort and a representative catch. Whereas UVC provided less variable estimates of relative density, controlled angling provided greater sampling efficiency. It is thus recommended that the two methods be used in conjunction. The optimal sampling protocols identified are suitable for rapid assessments or long-term monitoring of subtidal, temperate reef fish communities.

Effects of fishing on a temperate reef community in South Africa 1: ichthyofauna

Exploitation of temperate reef fish not only affects the target species but potentially changes the composition of reef fish assemblages. This study investigated the effect of fishing on the ichthyofaunal community at protected and exploited sites around the Goukamma Marine Protected Area (MPA) on the South African temperate south coast. Abundance and size frequency data from 273 standardised angling and 44 underwater visual census sites were analysed with generalised linear modelling and multivariate techniques to separate the effects of exploitation, habitat, time of day and season. Ichthyofaunal communities differed significantly between protected and exploited sites, which is likely a result of differential fishing pressure. Abundance and size of roman Chrysoblephus laticeps, the dominant species of the local linefishery, were significantly lower at exploited sites. Non-target species with considerable dietary overlap with roman were significantly less abundant inside the MPA, probably due to interspecific competition, whereas species whose diets differed to that of roman were more abundant at protected sites. The results show that fishing can have an influence on the composition of target and non-target species and that these effects need to be considered in fisheries management and conservation planning.

The effect of marine protected areas on an exploited population of sex-changing temperate reef fish: an individual-based model

The effect of two marine protected areas (MPAs) on roman Chrysoblephus laticeps (Sparidae), an exploited reef-fish species inhabiting the South African temperate south coast, was simulated with a spatially explicit, individual-based model based on geographically correct habitat distribution. The model domains were small compared with the dispersal range of pre-recruits, and recruitment was held constant. Adult fish movement rules were based on the results of high-resolution mark-and-recapture and telemetry studies. Fish densities, age-structure and life-history parameters were derived from comprehensive underwater surveys and biological analyses. The model included the effect of fishing on size-at-sex change. The results indicate a recovery of fish abundance-per-recruit, size frequency and sex ratio to, or close to, pre-exploitation levels within the protected areas 10 years after the implementation of both MPAs. Results suggest that, for resident species such as roman, even small MPAs (6 km2) can offer protection. The small exchange of post-recruit fish into the adjacent areas results in negligible improvement (1%) of catches. The MPAs support more and larger spawning fish, which may improve recruitment into adjacent fished areas

The process of developing a management system for subsistence fisheries in South Africa: recognizing and formalizing a marginalized fishing sector in South Africa

Subsistence fishers were first recognized as a formal fishing sector in South Africa when new fishing legislation, aimed at redressing past inequalities, was enacted in 1998. Little information was available about these fishers, their activities, and the resources upon which they rely. Recognizing the imperative to gain an understanding of the fishers and to consult broadly, the national agency responsible for the management of marine living resources, Marine and Coastal Management (MCM) of the Department of Environmental Affairs and Tourism, appointed a Subsistence Fisheries Task Group (SFTG) in December 1998 to provide advice on the implementation of appropriate management systems for subsistence fisheries. This paper describes the process followed to formulate recommendations that were presented by the SFTG to MCM in February 2000. The activities of the SFTG fell into two categories: research aimed at identifying subsistence fishers and gaining an understanding of their activities and socio-economic profiles; and consultation aimed at ensuring that the needs and aspirations of fishers and the experience of local managers were incorporated. Research included both field-based studies and synthesis of information about comparative fisheries elsewhere. Consultation took the form of local interviews and focus-group discussions, meetings with fishers and a national workshop. A pivotal activity was the development of a clear definition and qualifying criteria for subsistence fishers. A significant outcome was the identification of a separate small-scale commercial sector, previously erroneously lumped with subsistence fishers. Needs of fishers and problems identified during the process provided the basis for recommendations in the following areas: definitions, assessment and categorization of resources, management systems, communication mechanisms, application and allocation procedures, capacity building, compliance, research and monitoring, and funding and staff required for the management of this new sector. An evaluation is made of the opportunities presented by the SFTG process, constraints experienced and lessons learnt, giving important insights that are applicable to other similar processes, yet seldom documented in formal literature.

Using baseline biological and ecological information to design a Traffic Light Precautionary Management Framework for leerfish Lichia amia (Linnaeus 1758) in southern Angola

The coastline of southern Angola is sparsely populated and, largely because of a protracted civil war, has very lightly exploited inshore fish stocks. This has provided the almost unprecedented opportunity to determine prefishing-state reference points and to implement management strategies at the early stages of exploitation. The leerfish Lichia amia is distributed from the Mediterranean Sea, along the west coast of Africa to the southern and eastern coasts of South Africa. Despite its importance in recreational catches in South Africa and Angola, there is little information on the biology of this species. The leerfish is one of the three most dominant recreational shore-fishery species in southern Angola, and a biological study on the species was conducted in that region between May 2005 and December 2006. The mean length of captured fish was 767 mm fork length (FL) and 6.8 kg, and the catch per unit effort was 0.13 fish angler−1 h−1 and 0.79 kg angler−1 h−1. The growth of the leerfish population (in mm) was described by: L t = 1 137(1 − e0.22(t + 1.58)), and its total mortality was estimated to be 0.41 (±0.05). Female mortality (0.40 ± 0.06) was lower than that for males (0.44 ± 0.14), and the length and age-at-50% maturity was 623 mm FL and 2.4 years respectively. Female fish with ripe ovaries were found between June and November. The male:female ratio was 1:1.9. Leerfish fed exclusively on fish, mainly sardinella Sardinella aurita (62% frequency of occurrence). Based on this biological information, a theoretical Traffic Light Precautionary Management Framework is constructed for the species. Appropriate management regulations and potential future threats to the species are discussed.

Comparison of the effects of different linefishing methods on catch composition and capture mortality of South African temperate reef fish

The effects of hook size, bait type, water depth and fishing effort on the selectivity and capture mortality of reef fish were investigated in a standardised fishing experiment on the temperate south coast of South Africa. A total of 2 406 fish was caught at 273 stations, distributed according to a random-stratified design. Generalised linear models separated the influences of environmental factors such as depth, temperature and season from the effects of fishing methods on catch rates and capture mortality. Dominant reef predators and larger individuals within species were more frequently caught on large hooks and sardine Sardinops sagax bait. The main cause for capture mortality was gut-hooking, aggravated by increased capture depth. Large roman Chrysoblephus laticeps were more frequently gut-hooked than small individuals. More roman were caught early in the fishing session and the average size of captured roman increased slightly during fishing sessions. The selection of legal-sized target fish can be increased by about 23% and immediate capture mortality of undersized fish can be reduced by 50% by using large hooks and sardine bait and by fishing for less than one angler-hour per station in water shallower than 20m. The results are useful for planning fisheries independent catch per unit effort surveys and for developing rules for catch-and-release competitions.