The status of the South African beach-seine and gill-net fisheries

Initial estimates indicate that there are at least 7 000 fishermen active in fisheries using beach-seine and gill nets in South Africa, mostly (86%) along the West and South coasts. Those fishermen utilize 1 373 registered and 458 illegal nets and report an average catch of 1 600 tons annually, constituting 60% harders Liza richardsonii, 10% St Joseph shark Callorhinchus capensis and 30% “bycatch” species such as galjoen Dichistius capensis, yellowtail Seriola lalandi and white steenbras Lithognathus lithognathus. Catch composition by mass variesbetween 70, 74 and 90% L. richardsonii off the Western, Southern and Eastern Cape coasts respectively to 88% sardine Sardinops sagax in KwaZulu-Natal. Catch-per-unit-effort declines eastwards from 294 and 115 kg.net-day-1 for the beach-seine and gill-net fisheries respectively off the West Coast to 48 and 5 kg.net-day-1 off KwaZulu-Natal. Consequently, the fishery changes in nature from a largely commercial venture on the West Coast to an artisanal/subsistence fishery on the East Coast. Attempts to validate compulsory catch returns indicate that at least half the annual catch, notably bycatch, is not reported. Reasons for this indicate an unwillingness to declare prohibited species, perceived avoidance of the taxman, ignorance as to the importance of catch statistics, multiplelicensing authorities and management inadequacy to police illegal catches and nets

Bycatch in the gillnet and beach-seine fisheries in the Western Cape, South Africa, with implications for management

Interview questionnaires and access point surveys were conducted in order to describe and quantify the catch composition of the inshore net-fisheries in the Western Cape, South Africa. A total of 138 562 fish, representing 29 species from 20 families, was recorded in 141 monitored commercial gillnet fishing operations between February 1998 and October 1999. Numerically, the legal target species, harders Liza richardsonii, dominated the catches, contributing 94.87% of the total gillnet catch. Elf, Pomatomus saltatrix, horse mackerel Trachurus trachurus capensis, gurnard Chelidonichthys capensis and barbel Galeichthys feliceps were the most common bycatch species, and contributed 4.2% to the total catch numerically and occurred in 12–47% of the marine 44–64-mm gillnet catches that were monitored. Five species most frequently targeted by shore-anglers on the West Coast: galjoen Dichistius capensis, white stumpnose Rhabdosargus globiceps, hottentot Pachymetopon blochii, silver kob Argyrosomus inodorus and white steenbras Lithognathus lithognathus, also occurred in gillnet catches. Most of the bycatch consisting of immature, undersized fish that were often injured during entanglement and were not released alive. L. richardsonii also numerically dominated the beach-seine hauls that were monitored (>99%) with only four bycatch species being recorded in low numbers. Beach-seine questionnaire respondents, however, reported sporadic catches of at least 17 bycatch species, including occasional appreciable catches of the important linefish species L. lithognathus and A. inodorus.Keywords: beach-seine, bycatch, catch composition, gillnets, fishery management, inshore netfishingAfrican Journal of Marine Science 2002, 24: 227–24

Catch-and-effort estimates for the gillnet and beach-seine fisheries in the Western Cape, South Africa

Total catch and effort for the inshore net-fisheries in the Western Cape, South Africa, were estimated by means of face-to-face questionnaire, telephone and access point surveys, analysis of factory records and compulsory catch returns. In most areas, gillnet fishing effort was confined to summer, with highest average catch per unit effort during months of low effort. Records of monofilament gillnet sales show that approximately 180 illegal nets are sold annually (20% of all sales). During the period 1994–1999, only 26 illegal mesh size nets were confiscated annually (14% of those sold) on average, indicating that few illegal fishers are apprehended. Beach-seine fishers appeared to operate opportunistically throughout the year along the West Coast, whereas South-West Coast permitholders concentrate their activity during summer. Sources of survey error in effort and catch-rate estimation are discussed. Approximately 25 000 gillnet days and 3 200 beach-seine hauls made annually land around 6 000 tons of fish, substantially more than the mean annual reported catch of 1 369 tons. Comparison of observed or documented catches with compulsory catch returns confirmed that as little as 21% of the actual effort and only 8% of the fish caught are reported. Despite the fact that catches are much greater than those reported, the lower catch rates, smaller average size of fish caught and historical and anecdotal evidence suggest that the harder Liza richardsonii stock is regionally overexploited in areas with high fishing effort. It is concluded that the inshore net fishery in the Western Cape is oversubscribed in most regions and a reduction in latent and “recreational” effort is therefore recommended. A suitable reduction in total effort may allow the L. richardsonii stock to recover, reduce the ecosystem effects of the fishery by reducing the amount of bycatch and improve catch rates for bona fide commercial fishers. It would also facilitate improved monitoring and policing of the fishery and hopefully improve compliance with regulations. Keywords: beach-seine, catch-and-effort estimates, catch returns, gillnets, Liza richardsoniiAfrican Journal of Marine Science 2002, 24: 205–22

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 catchand-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 betweenApril 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. Fromthe 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 WestCoast (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 effort was estimated at 3.2×106 angler days.year–1 and the total catch was estimated at 4.5×106 fish.year–1 or 3 000 tons.year–1. Targeted species varied regionally, with elf Pomatomus saltatrix (29%) being the most sought after species on the KwaZulu-Natal coast, kob Argyrosomus japonicus (18%) on the Eastern Cape coast and galjoen Dichistius capensis on the Southern Cape coast (30%) and along the West Coast (50%). The catch composition by mass was dominated byP. saltatrix on the KwaZulu-Natal coast (29%), the Eastern Cape coast (26%), and on the Southern Cape coast (56%) and by white stumpnose Rhabdosargus globiceps (40%) on the West Coast. Although anglersgenerally supported the regulations currently governing the linefishery, the questionnaire results showed that knowledge and compliance of them was poor. A low level of law enforcement was found, except for inKwaZulu-Natal. Management of the linefishery is discussed in relation to the findings of this study

An economic valuation of the South African linefishery

Economic data collected during 1995 and 1996 in a national survey of shore-anglers and skiboat fishermen is used to provide an economic assessment of aspects of recreational, subsistence and commercial linefishing on the South African coastline. Results show that more than 90% of shore-anglers have incomes which lie in the highest two quintiles of the distribution of incomes, and tha

Assessment of the conservation priority status of South African estuaries for use in management and water allocation

The future health and productivity of South Africa's approximately 250 estuaries is dependent on two main factors: management and freshwater inputs. Both management and water allocation decisions involve trade-offs between conservation and various types of utilisation. In order to facilitate decision-making in both of these spheres, it is necessary to understand the relative conservation importance of different estuaries. This study devises a method for prioritising South African estuaries on the basis of conservation importance, and presents the results of a ranking based on the collation of existing data for all South African estuaries. Estuaries are scored in terms of their size, type and biogeographical zone, habitats and biota (plants, invertebrates, fish and birds). Thirtythree estuaries are currently under formal protection, but they are not representative of all estuarine biodiversity. We performed a complementarity analysis, incorporating data on abundance where available, to determine the minimum set of estuaries that includes all known species of plants, invertebrates, fishes and birds. In total, 32 estuaries were identified as 'required protected areas', including 10 which are already protected. An estuary's importance status (including 'required protected area' status) will influence the choice of management class and hence freshwater allocation under the country's new Water Act, and can be used to assist the development of a new management strategy for estuaries, which is currently underway. WaterSA Vol.28(2) 2002: 191-20

Isothiocyanate NB7M causes selective cytotoxicity, pro-apoptotic signalling and cell-cycle regression in ovarian cancer cells

The present report identifies indole-3-ethyl isothiocyanate NB7M as a potent cytotoxic agent with selective activity against cell lines derived from various tumour types. Ovarian cancer cell lines showed sensitivity to NB7M (60–70% cytotoxicity at 2.5 μM), in contrast to control cells (TCL-1 and HTR-8; IC50 ∼15 μM). In a screen performed by the National Cancer Institute (NCI) (NCI60 cancer cell-line assay) NB7M (NSC746077) reduced growth up to 100% with an IC50 between 0.1 and 10 μM depending on the cell line studied. Using SKOV-3 ovarian cancer cells as a model, mechanisms of cytotoxicity were analysed. NB7M caused hallmarks of apoptosis such as PARP-1 deactivation, chromatin condensation, DNA nicks, activation of caspases-9, -8, -3, loss of mitochondrial transmembrane depolarisation potential and upregulation of pro-apoptotic mitogen activated protein kinases (p38, SAP/JNK). NB7M downregulated phosphorylation of prosurvival kinases (PI-3K, AKT, IKKα), transcription factor NF-κB, and expression of DNA-Pk and AXL receptor tyrosine kinase. Subcytotoxic doses of NB7M inhibited DNA synthesis, caused G1-phase cell-cycle arrest and upregulated p27 expression. The present report suggests that NB7M is a selective cytotoxic agent in vitro for cell lines derived from ovarian and certain other tumours. In addition, NB7M acts as a growth/cell-cycle-suppressing agent and may be developed as a potential therapeutic drug to treat ovarian cancer

Review of the projected impacts of climate change on coastal fishes in southern Africa

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

White shark and other chondrichthyan interactions with the beach-seine (treknet) fishery in False Bay, South Africa

Public perception has been that an apparent increase in the nearshore occurrence of white sharks Carcharodon carcharias in False Bay, on the south coast of South Africa, can at least be partly attributed to beach-seine (treknet) operations attracting sharks into this coastal area. To assess the merit of these concerns, all available beach-seine catch-and-effort data from the False Bay fishery over a 32-year period were analysed. A total of 27 cartilaginous species from 15 families was recorded in around 11 400 hauls from 1974 to 2006. Most (98%) of these comprised small benthic invertebrate feeders such as smooth houndshark Mustelus mustelus and lesser guitarfish Rhinobatos annulatus. Large sharks such as C. carcharias and ragged-tooth shark Carcharias taurus were rare, occurring i