Catch and effort of the shore and skiboat linefisheries along the South African Eastern Cape Coast

An assessment of catch and effort in the Eastern Cape shore and skiboat linefisheries was undertaken between 1994 and 1996 by means of roving creel and access point surveys. Catch-and-effort data were obtained from direct observation of 3 273 shore-fishers, 172 recreational and 223 commercial skiboat outings. Total effort in the region was high at 903 186 fisher-days year^?1 in the shore fishery and 64 266 and 24 357 fisher-days year^?1 in the commercial and recreational skiboat sectors respectively. The fisheries are multispecies in nature. The shore fishery consisted of 66 species, the recreational skiboat fishery 44 species and the commercial skiboat fishery 48 species. Just 10 species accounted for 75, 83 and 90% of the catch of the shore, recreational and commercial skiboat fishery respectively. The average catch per unit effort (cpue) was low in all sectors, 1.15 kg fisher^?1 day^?1 in the shorefishery, 9.4 kg fisher^?1 day^?1 in the recreational skiboat fishery and 21.5 kg fisher^?1 day^?1 in the commercial skiboat fishery. Catch data showed that professional and club anglers are more successful fishers. Comparisons with historic records for Port Elizabeth revealed that the cpue in the shore fishery had declined markedly, whereas the total effort increase was negligible (0.1%). In addition, the species composition of the fishery has changed.     

Spatial and seasonal distribution patterns of the ragged-tooth shark Carcharias taurus along the coast of South Africa

Catches from competitive shore-anglers, inshore boat-based anglers and sightings by spearfishers and divers were used to infer the spatial and seasonal movement patterns of young-of-the-year (<1.2m TL), juvenile (1.2–1.8m TL), sub-adult (1.8–2.4m TL) and adult (>2.4m TL) ragged-tooth sharks Carcharias taurus along the coast of South Africa. Adult sharks inhabited the entire coast between Maputaland in the east and St Helena Bay on the West Coast. The geographical range of sharks at earlier life-history stages decreased with size. The vast majority (93.8%) of young-of-the-year sharks recorded from competitive shore-angling club records were between East London and St Francis Bay on the East Coast, suggesting this region to be the primary nursery area for C. taurus. Estuarine systems, although utilised by young-of-the-year and juvenile C. taurus, do not form an important component of their nursery area in South Africa. Catches of pregnant and post partum females taken during the same time of year and in different areas indicated a biennial reproductive cycle. C. taurus appears to display a high degree of affinity for particular reefs. The reason some reefs are chosen over others, despite having similar physical characteristics, remains unclear. A significant increase in the number of C. taurus caught in competitions held by the Border Rock and Surf Angling Association between 1984 and 2004 suggests an increase in the abundance of C. taurus.     

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 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 by P. 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 anglers generally 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 in KwaZulu-Natal. Management of the linefishery is discussed in relation to the findings of this study.     

Growth of spotted ragged-tooth sharks Carcharias taurus (Rafinesque) in captivity

Eight spotted ragged-tooth sharks Carcharias taurus (95–248,4 cm total length TL), ranging in known age from 0 to 16,6 years, were used to investigate the growth of the species in captivity. Total length was measured by a standard technique in some cases and estimated from photographs in others. The accuracy of the photographic technique was evaluated and found adequate for captive growth studies in sharks. Parameters of various growth models were estimated by non-linear regression and the special Von Bertalanffy growth model provided the best fit to the age-length data of the combined sexes. The parameters of the special Von Bertalanffy model are L _∞ = 249,8 cm TL, K = 0,233·year^?1, t ₀ = ?2,238 years. Longevity of captive C. taurus is greater than 16,6 years.     

Sharks caught in the protective gill nets off KwaZulu-Natal,South Africa. 8. The Great hammerhead shark Sphyrna mokarran (Rüppell)

Between 1978 and 1993, 209 great hammerhead sharks Sphyrna mokarran were caught in the shark nets which protect the swimming beaches of KwaZulu-Natal. This species constituted 0,97% of the total shark catch, with a mean annual catch of 13. Catch rates showed a significant decline during the period under review, from 0,66 to 0,09 sharks·km-net^?1·year^?1. Most sharks were caught in the north of the netted region between January and May. Catches at Mzamba, the southern extremity of the netted region, represent the southernmost records of this species on the east African coast. The males ranged in size from 106 cm precaudal length (18 kg) to 264 cm (220 kg) and females from 140 cm (35 kg) to 326 cm (400 kg). Males matured at about 217 cm and females at 237 cm. Very few sharks were found in mating condition. Elasmobranchs were found in 82% of non-empty stomachs. There was a high incidence of stingrays (Dasyatidae), guitarfish (Rhinobatidae) and other bottom-dwelling fish in the diet.     

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 in <0.2% of hauls. The only medium to large sharks that occurred frequently (15% of hauls) in any appreciable numbers (0.3 per haul) were bronze whalers Carcharhinus brachyurus. The relatively high numbers of C. brachyurus compared with C. carcharias, their overlapping size distributions and the difficulty of identifying sharks from a distance, suggests that many of the sharks observed following beach-seine nets are the bronze whalers. Overall, the frequency of occurrence of C. carcharias in the nets is much lower than would be predicted from the high number of observations in the nearshore region. Furthermore, beach-seine fishing rights in False Bay have been reduced from around 170 in the 1970s to five at present. There has been no corresponding decrease in shark incidents. On the contrary, shark incidents have increased from two in the 1970s to six during the period 2000–2005. Overall, there appears to be no strong link between beach-seine activity and human incidents with white sharks in False Bay.     

Sharks caught in the protective gill nets off Natal,South Africa. 5. The Java shark Carcharhinus amboinensis (müller & Henle)

Between 1978 and 1990, 209 Java sharks Carcharhinus amboinensis were caught in the shark nets that protect the swimming beaches of Natal, thereby constituting 0,5 per cent of the total shark catch. The catch rate was relatively constant at about 0,4 sharks·km net^?1·year^?1. Catches were highest at the northernmost beaches in summer and autumn and they consisted mostly of juvenile, but not newborn, and adolescent sharks. Specimens ranged from 99 to 176 cm PCL, with a mode of 131–135 cm for males and 131–145 cm for females. Males matured at 150 cm and females at 160 cm. Of the eight mature females caught, five were pregnant. Mating takes place in late summer and gestation is thought to last approximately 12 months. The largest embryo found was 53 cm. Teleosts were identified in 62,1 per cent of the 103 stomachs that contained food. Elasmobranchs (44,7%), crustaceans (12,6%) and cephalopods (11,6%) were the other major prey groups. Most of the fish prey were demersal, associated with soft bottoms.     

Attitudes and perceptions influence recreational angler support for shark conservation and fisheries sustainability

Despite the perilous status of many shark populations, rallying support for their conservation has been challenging, due in part to both long held negative perceptions and desire for shark fisheries. Recreational anglers are often advocates of conservation and can act as valuable partners with resource managers in developing fisheries management and conservation strategies. However, understanding their attitudes and perceptions, particularly towards resource status and management, is essential to developing successful management strategies and predicting outcomes. As a case study for assessing the complex challenges of sustainable shark fisheries, Florida recreational anglers were surveyed to understand how attitudes and perceptions influenced their willingness to donate for shark 1) conservation and protection or 2) fisheries sustainability. Overall, recreational angler willingness to donate was 25.5%, but attitudes and perceptions helped explain dramatic divides. For instance, willingness to donate was only 6% among the subset of anglers that perceived a growing large coastal shark population as a threat to recreational fishing opportunities. Highest support for shark conservation was shown by anglers who value seeing sharks in the wild (41.4%), and even more so among individuals who occasionally target sharks while fishing recreationally (65.8%). Pervasive among anglers unwilling to donate was a perception that shark populations were increasing, and thus not in need of further protection. These findings illustrate attitudes and perceptions that challenge shark conservation and fisheries management, as well as the critical importance of engaging anglers when developing strategies that rely on the recreational angling community for support.     

Sharks caught in the protective gill nets off Natal,South Africa. 4. The bull shark Carcharhinus leucas Valenciennes

A total of 772 bull sharks Carcharhinus leucas was caught in Natal's protective "shark nets" between 1978 and 1990. Confusion in distinguishing C. leucas from C. amboinensis resulted in their catch data being combined from 1966, when data collection began, to 1977. The catch rate of the species pair declined until 1977, recovered until the mid 1980s, but subsequently declined again. The trend in catch rate of C. leucas alone for the period 1978–1990 was similar, with minima of 0,70 sharks·km-net^?1·year^?1 in 1978 and 0,95 in 1990, and a maximum of 2,08 in 1986. Recaptures of six tagged sharks suggest that the species is not highly migratory. Catches, particularly of immature sharks, were highest at the northernmost beaches. Most bull sharks were caught in summer and in turbid water (mean water clarity 2,0 m). The sex ratio of the catch was 1 male to 1,3 females. Sizes ranged from 74 to 213 cm precaudal length, with modes of 141–145 cm (males) and 171–175 cm (females). Size at maturity for both sexes was between 180 and 190 cm. The mating season was prolonged but with a summer peak. Seven gravid females were examined; the mean litter size was 8,7 embryos and size at birth was approximately 55 cm. Fluke infections were observed on 9 per cent of animals examined. As size increased there was a shift in diet, in terms of frequency of occurrence, from teleost to elasmobranch predominance. There was a high incidence of benthic and demersal species in the stomachs. Minor prey groups included mammals, birds, turtles, molluscs and crustaceans. Scavenging appeared to be important.     

Population size of neonate and juvenile dusky sharks Carcharhinus obscurus in the Port of Ngqura,South Africa

Identifying nearshore waters that serve as important habitats for neonate and juvenile sharks is crucial for effective fisheries management. This study examined the abundance of neonate and juvenile dusky sharks Carcharhinus obscurus within the Port of Ngqura, on the south-east coast of South Africa, between September 2006 and August 2007 using a combination of shore-angling catches and mark-recapture data. During this period, the port was non-operational and still undergoing construction. A total of 480 dusky sharks, ranging in size from 50 to 123 cm (precaudal length), was captured. Catch per unit effort was greatest between October and February, peaking in November at 0.51 sharks angler^–1 h^–1. Of the 219 C. obscurus tagged and released during the study period, 37 (16.9%) were recaptured. Sharks were at liberty from 0 to 409 days with the majority (89.2%) recaptured within the port. Using a Jolly-Seber open population model, the abundance of sharks within the port was estimated at 552 (95% CI: 422–765). Annual apparent survival probability was 0.38 (95% CI: 0.30–0.46), with an average annual recapture probability of 0.28 (95% CI: 0.19–0.39). This study demonstrates that the Port of Ngqura is an important summer habitat and core activity zone for both neonate and juvenile dusky sharks.     

Distribution,seasonality, lengths,and feeding behaviour of whale sharks (Rhincodon typus) observed in New Zealand waters

Data from 36 whale shark (Rhincodon typus Smith, 1828) sightings off north‐east North Island, New Zealand are summarised. Sightings were concentrated over the outer shelf and shelf break in areas influenced by the East Auckland Current at sea surface temperatures (SST) of 21–24°C. Sightings occurred from late spring to early autumn (November‐April) but were most frequent in midsummer (February) when upwelling along the north‐east shelf is weakest. The data indicate whale sharks occur off north‐east New Zealand most summers, including those when SST is colder than usual. A cluster of sightings and three observations of whale sharks feeding on schools of anchovy (Engraulis australis) near Whale Island, Bay of Plenty, suggest whale sharks may aggregate seasonally in this area. Estimated total lengths (TL) of 26 whale sharks ranged from 3.5 to 15 m, with 73% between 6 and 9 m TL.     

Socio-economic aspects of the tiger shark diving industry within the Aliwal Shoal Marine Protected Area,South Africa

Understanding socio-economic aspects of the tiger shark Galeocerdo cuvier diving industry, including information on participant expectations, experiences and expenditure, is necessary for the effective management of the Aliwal Shoal Marine Protected Area on the east coast of South Africa. Between January and December 2007, a total of 2 133 tiger shark dives was conducted by 1 065 divers (95% CI = 946-1 198). Data were collected by means of the administration of a semi-structured survey questionnaire to 197 (18.6%) dive participants. Respondents indicated that the direct value of tiger shark diving to the Aliwal Shoal region was R12 405 274 (95% CI = R10 777 324-14 228 541). A total of 1 000 Monte Carlo simulations was used to estimate confidence intervals. On a ranking from one (poor) to five (excellent), the average participant response to overall quality of dive and standard of dive operator was 4.6 and 4.7 respectively. The majority of divers (98.0%) observed a tiger shark, at an average of four per dive. Although tiger sharks approached to an average distance of 1.6 m from divers, the majority (95.9%) felt safe and enjoyed the experience. The majority of interviewees (88.5%) supported the use of chumming for a closer ‘tiger shark experience’.     

Spatio‐temporal dynamics and biomass of Cymodocea nodosa in Bekalta (Tunisia,Southern Mediterranean Sea)

Leaf growth, biomass and production of Cymodocea nodosa were measured from October 2006 to September 2007 in Monastir Bay (Tunisia). Shoot density showed a clear seasonal pattern, increasing during spring and summer and decreasing during fall and winter. Monthly mean shoot density ranged between 633 ± 48 and 704 ± 48 shoots?m^?2. The monthly average total biomass ranged between 560 ± 37 and 646 ± 32 g dry weight (DW)?m^?2. Total biomass varied significantly among stations and sampling times but did not show seasonal variation. Leaf plastochrone intervals varied seasonally, with an annual average of 28–30 days. Leaf productivity was highest in August (2.61 g DW?m^?2?day^?1) and lowest in February (0.35 g DW?m^?2?day^?1). Annual belowground primary production varied from 263 to 311 g DW?m^?2?year^?1. Annual leaf production was approximately equal for all the stations (from 264 to 289 g DW?m^?2?year^?1). Variability in water temperature, air temperature and salinity explained the annual variability in biological characteristics. Changes in belowground and total biomass were not correlated with seasonal variability in the environmental parameters monitored. Additionally, a literature review was conducted of C. nodosa features at other Mediterranean sites, encompassing 30 studies from 1985 to 2014.     

White sharks Carcharodon carcharias at Bird Island,Algoa Bay,South Africa

We present the first quantitative study of the occurrence, size and sex of white sharks Carcharodon carcharias at Bird Island, Algoa Bay. Twenty-two boat trips were made to Bird Island between November 2009 and October 2011 to chum for sharks. A total of 53 sharks was observed over the study period, ranging in size from 1.5 to 4.5 m total length (TL) and with the majority (60.3%) being <3 m TL. The sex ratio of sharks for which sex could be determined was not significantly different from unity. In both study years, sharks were present only in the winter between April and November with a maximum of 1.2 sharks sighted per hour. A zero-altered model, comprising a logistic regression to model presence/absence and a log-normal generalised linear model for abundance, showed that season explained the presence of sharks, peaking in mid-July, with abundance being significantly higher with higher barometric pressure. This study identified Bird Island as an important white shark aggregation site on the east coast of South Africa. These data are crucial not only to improve our understanding of white shark seasonal distribution and biology, but also for the long-term management and conservation of the species in South Africa.     

Biological parameters reflecting the current state of the exploited pink dentex Dentex gibbosus (Pisces: Sparidae) population off the Canary Islands

A total of 639 pink dentex Dentex gibbosus was collected in Canary Islands waters between April 1991 and September 1993. Total lengths ranged from 14,2 to 95,2 cm. Females dominated smaller size-classes and males the larger ones. The species was characterized by protogynous hermaphroditism. The overall ratio of males to females was 1 : 1,45. The reproductive period extended from April to September, spawning peaking in June/July. The total lengths at 50% maturity were 34,7 cm for females and 38,6 cm for males. The length-mass relationship for the whole sample can be described by the parameters a = 0,01014 and b = 3,0812. Fish aged 0–16 years were present in the samples. The parameters of the Von Bertalanffy growth equation were: L _∞ = 101,2 cm, k = 0,149·year^?1, and t ₀ = ?0,111 years. The rates of total mortality Z and natural mortality M were 0,57 and 0,28·year^?1 respectively. Rates of fishing mortality F and exploitation E were 0,29 and 0,51·year^?1 respectively. The estimated length at first capture (LC ₅₀) was 17,8 cm total length.     

Role of Zooplankton in the Vertical Mass Flux in the Kara and Laptev Seas in Fall

The role of zooplankton in the vertical mass flux in the Kara and Laptev seas was studied during cruise 63 of the R/V Akademik Mstislav Keldysh in August–October 2015. Mass fluxes were estimated using sediment trap samples. The maximum values of the total vertical flux (19600 mg m^?2 day^?1) and particulate organic carbon (POC) flux (464 mg C m^?2 day^?1) were measured close to the Lena River Delta in the Laptev Sea. In the Kara Sea, the total flux (80–2700 mg m^?2 day^?1) and the POC flux (17–130 mg C m^?2 day^?1) were substantially higher than the estimates published earlier. The fecal pellet flux varied from 2 to 92 mg C m^?2 day^?1 and made up 4–190% of the total organic carbon flux. The mineral composition of fecal pellets largely mirrored that of suspended particulate matter. Clay minerals in the fecal pellets were more abundant than in particulate matter in the areas with noticeable freshwater impact. The flux of zooplankton carcasses varied from 0.1 to 66.4 mg C m^?2 day^?1 and made up 0.2–72% of total POC flux. The results are discussed in relation to the abundance and composition of zooplankton, the concentration and composition of suspended particulate matter, hydrophysical conditions, and methods of sample preparation for analysis.     

Illegal shark fishing in the Galápagos Marine Reserve

Illegal shark fishing is thought to occur globally, including within so-called “shark sanctuaries”, marine reserves and even inside UNESCO World Heritage sites, such as the Galápagos Islands. Presumably, this is due to poor local enforcement coupled with the growing international demand (and high economic incentives) for shark and other wildlife products. Understanding illegal shark fishing practices, and specifically catch composition, is important as poaching is identified as a causal factor of global declines in shark populations. Unfortunately, reliable quantitative data on illegal shark fishing are scarce. Here, the catch onboard an illegal shark fishing vessel seized within the borders of the Galápagos Marine Reserve was documented. A total of 379 sharks from seven shark species were found onboard the vessel. A large fraction of the illegal catch was comprised of both female and juvenile sharks (64% and 89%, respectively). Despite numerous recent advances in shark conservation worldwide, this study demonstrates illegal shark fishing is an ongoing concern and that stricter enforcement and legislation is urgently needed, particularly in areas of high biodiversity.     

Sharks caught in the protective gill nets off Natal,South Africa. 6. The copper shark Carcharhinus brachyurus (Günther)

Between 1978 and 1990,1 800 copper sharks Carcharhinus brachyurus were caught in the shark nets that protect the swimming beaches of Natal. The species constituted 9,6 per cent of the total shark catch. Annual catches and catch rates fluctuated widely about a mean of 138 sharks and 3,5 sharks·km net^?1 respectively. Most sharks were caught at the southern beaches during the annual Natal sardine run in June and July, when shoals of pilchard Sardinops ocellatus move into the waters off southern Natal. Catches were dominated by sharks >140 cm pre-caudal length PCL. Mature males (generally ≥ 175 cm PCL) were present for much of the year, but mature females (generally ≥ 190 cm) and immature sharks were only abundant in June and July. Gonad indices in males were highest in March and April, whereas high gonad indices and large ova were recorded in females in June and July. Mating appears to take place after July and parturition about 12 months later, both occur south of the netted region. The smallest of 50 pregnant females caught was 178 cm. Mean embryo length within a litter ranged from 17 to 54 cm. Teleosts were found in 92 per cent and pilchard in 84 per cent of stomachs containing food.     

Actions speak louder than words: Tournament angling as an avenue to promote best practice for pelagic shark fishing

Social research can aid in understanding the behaviour of the general public or stakeholders towards natural resources. In the case of recreational fishing, social research aids in integrating anglers' knowledge and attitudes into management frameworks to increase the likelihood of the uptake of new management regulations. Tournament anglers were surveyed at game fishing competitions throughout New South Wales, Victoria, and South Australia between February 2012 and May 2013 to investigate their general beliefs around sharks and their behaviours when targeting pelagic sharks. Over half (55%) of the anglers interviewed practised catch and release of pelagic sharks. Of those, almost all (98%) asserted that they attempt to release sharks in good condition, but a large percentage of anglers (48%) did not use circle hooks that have been shown to increase post-release survival. Results showing some concordance between angler's beliefs and behaviours when targeting pelagic sharks suggest that anglers are cognisant of the functional role of sharks in the ecosystem and would be open to recommendations ensuring the long-term sustainability of recreational fisheries targeting pelagic sharks.     

Composition of elasmobranch landings in Bahrain

The first detailed elasmobranch fisheries data for the Kingdom of Bahrain are presented, based on surveys of fish markets in April 2012. At least 25 species were recorded, including undescribed taxa. The milk shark Rhizoprionodon acutus was the most frequently recorded species; together with the Arabian smoothhound Mustelus mosis and banded eagle ray Aetomylaeus nichofii, these species comprised 53% of individual abundance. Sharks were almost entirely small individuals <1 m total length (TL). Males of small shark species were largely mature, whereas nearly all individuals of larger sharks were immature. For several elasmobranch species, landings were significantly biased towards males, which were largely mature. The species assemblage showed some notable differences in composition to that of adjacent Qatar, sampled at the same time of year, highlighting the importance of local data collection.