The Red Sea has long been recognized as a global hotspot of marine biodiversity. Ongoing overfishing, however, is threatening this unique ecosystem, recently leading to the identification of the Red Sea as one of three major hotspots of extinction risk for sharks and rays worldwide. Elasmobranch catches in Saudi Arabian Red Sea waters are unregulated, often misidentified and unrecorded, resulting in a lack of species-specific landings information, which would be vital for the formulation of effective management strategies. Here we employed an integrated approach of fisheries dependent and independent survey methods combined with molecular tools to provide biological, ecological and fisheries data to aid in the assessment of the status of elasmobranch populations in the Red Sea. Over the course of two years, we conducted market surveys at the biggest Saudi Arabian fish market in Jeddah. Market landings were dominated by, mostly immature individuals - implying both recruitment and growth overfishing. Additionally, we employed baited remote underwater video (BRUVS) and longline surveys along almost the entire length of the Red Sea coast of Saudi Arabia as well as at selected reef systems in Sudan. The comparison of catch per unit effort (CPUE) data for Saudi Arabian Red Sea BRUVS and longline surveys to published data originating from non-Red Sea ocean systems revealed CPUE values several orders of magnitude lower for both survey methods in the Red Sea compared to other locations around the world. Finally, we infered the regional population structure of four commercially important shark species between the Red Sea and the Western Indian Ocean.We genotyped nearly 2000 individuals at the mitochondrial control region as well as a total of 20 microsatellite loci. Genetic homogeneity could not be rejected for any of the four species across the spatial comparison. Based on high levels of region-wide exploitation, we suggest that, for management purposes, the population structure of all four species should be considered as single stock in the three marginal seas surrounding Arabia. Overall, our combined results indicate a severe depletion of sharks in Saudi Arabian Red Sea waters, likely caused by drastic overfishing of elasmobranch populations.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Smoothhound sharks Mustelus mustelus (Chondrichthyes: Triakidae) were conditioned to associate a compound auditory and electrical conditioned stimulus (CS) using the presentation of food as the unconditioned stimulus (US). This was done to investigate the general conditioning process of sharks, specifically the use of conditioned stimuli, the time frame required for conditioning, the retention of conditioned responses and the individual learning capabilities of sharks in classical conditioning experiments. Conditioning was done in two CS experiment replicates, in which the CS and the US were paired to elicit a conditioned response (CR: entering of a feeding area). Shark behaviour in these replicates was compared with those of sharks in a CS control. In the CS control, the CS and US were not paired; consequently no CS-US association was formed. In contrast, half of the sharks in the 1st and 2nd CS replicates formed the conditioned CS-US association after five and six days of conditioning training, respectively. This conditioned association was also retained over a two-month rest period. However the rate of conditioning of sharks varied, which was thought to be due to differences in motivational drives, particularly hunger. These experiments demonstrated that classical conditioning could provide a mechanism whereby smooth hound sharks can adapt to utilise new food sources. However these experiments could not demonstrate whether auditory or electrical cues are more biological relevant signallers of the presence of food for smooth hound sharks. According to the "belonging ness" phenomenon, for conditioning to be successful, the CS should be biologically relevant to the US. Therefore by comparisons of the conditioning success with different conditioned stimuli, the biological relevance of each CS can be determined. To determine the biological relevance of each component of the compound CS, an auditory or electrical CS was paired with the presentation of food (US), in separate experiments. The conditioned CS-US association formed in the majority of the sharks after 60 and 57 conditioning trials in the auditory CS and electrical CS experiment, respectively. This suggests that both auditory and electrical cues are biologically relevant signallers of food, facilitating the oppurtunistic feeding behaviour of smoothhound sharks. However, after five days of conditioning, conditioning with the electrical CS had proceeded further and the electrical CS-US association was stronger than the auditory CS-US association. This indicates that electrical cues are more biologically relevant due to past feeding experiences. Thus, classical conditioning during past feeding experiences can influence the feeding behaviour of smooth hound sharks. / AFRIKAANSE OPSOMMING: Gladde-hondhaaie Muste/us muste/us (Chondrichthyes: Triakidae) is gekonditioneer om "n gekombineerde klank en elektriese konditionerings stimulus (CS) met voedsel, die ongekonditioneerde stimulus (US) te assosieer. Dit is gedoen om die konditionerings proses, spesifiek die gebruik van konditionerings stimuli, tyd benodig vir konditionering, behoud van die gekonditioneerde gedrag en individuele leer-vermoëens van haaie in klassieke konditionerings eksperimente te ondersoek. Konditionering is gedoen in twee CS eksperiment replikate, waarin die CS en die US saam aangebied is, om "n konditionerings reaksie (CR: om in 'n voedings area in te beweeg) teweeg te bring. Die gedrag van haaie in die CS replikate is vergelyk met die van haaie in "n CS kontrole. In die CS kontrole is die CS en die US nie saam aangebied nie en gevolglik is geen gekonditioneerde CS-US assosiasie gevorm nie. Daarenteen is die CS-US assosiasie by die helfte van die haaie in die 1st en 2de CS replikate gevorm, na vyf en ses dae, onderskeidelik. Hierdie gekonditioneerde CS-US assosiasie het selfs behoue gebly na 'n twee maande rus periode. Die tempo van konditionering het egter verskil, moontlik a. g. v. motiverings verskille, veral hongerte. Hierdie eksperimente het gedemonstreer dat klassieke konditionering kan dien as 'n meganisme waarmee gladde-hondhaaie kan aanpas om nuwe voedsel bronne te benut. Hierdie eksperimente kon egter nie demonstreer óf klank stimuli óf elektriese stimuli meer biologiese relevante seine van die teenwoordighied van voesel is vir gladdehondhaaie nie. Volgens die "belonging ness" verskynsel, moet die CS biologies relevant to die US wees, vir konditionering om suksesvol te wees. Dus kan die biologiese relevansie van verskillende konditionerings stimuli bepaal word deur die konditionerings sukses van elke CS te vegelyk. Om die meer biologiese relevante komponent van die gekombineerde CS te bepaal, is 'n klank of elektriese CS saam met voedsel aangebied in aparte eksperimente. Die gekonditioneerse CS-US assosiasie is gevorm by die meeste van die haaie na 60 en 57 konditionerings proeflopies in die klank en elektriese CS eksperimente, onderskeidelik. Hierdie resultate dui daarop dat beide klank en elektriese stimuli biologies relevante siene van voedsel is, wat die oppurtunistiese voedings wyse van gladde-hondhaaie fasiliteer. Konditionering met die elektriese CS het egter verder gevorder en die elektriese CS-US assosiasie was sterker as die klank CSUS assosiasie na vyf dae van konditionering. Dus, mag elektriese stimuli meer biologies relevant wees weens vorige voedings ervaringe. Dit illustreer dat klasseke konditionering tydens vorige voedings ervaringe die voedings gedrag van gladde-hondhaaie kan beinvloed.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The soupfin shark, Galeorhinus galeus, is a circum-global shark species of great economical importance. Their reproductive biology is reasonably well understood, but intraspecific differences between global populations necessitate the study o f populations separately. For this study, 70 male and 74 female specimens were collected along the southwestern coast of South Africa between 34°8'S; 18°27'E and 34°24S; 21°25'E. Morphological changes were described and serum steroid hormone concentrations evaluated by enzyme-linked immunosorbent assay (ELISA) over an almost-complete reproductive cycle. Males display an annual spermatogenic cycle that starts with a significant peak in testosterone concentrations coinciding with the start o f spermatogenesis around April-May. Testosterone levels decrease to reach a minimum in late-winter after which spermiogenesis commences. The prevalence of spermiogenic cysts in the testis increase to reach a peak between February and April, after which mating occurs until about July. Females (aplacentally viviparous) are suggested to have a triennial cycle, similar to the Brazilian & Australian populations, but different from the Californian & Mediterranean populations. During the first year after parturition there is not much reproductive development. The following year sees increased vitellogenic activity in ovarian follicles and development of the oviducal glands and uteri. Ovulation then occurs towards the end of that year. Mating is suggested to precede ovulation by two to three months necessitating sperm storage by the females in their oviducal glands. A 12-15 month gestation ensues and ends in parturition the following summer. Testosterone and estradiol levels fluctuate together and are involved in the preparation for ovulation and oviducal gland development. Progesterone levels show two distinct peaks during the year, in both immature and mature females, and could not yet be functionally linked to any reproductive activity or condition. This cycle is not very tightly synchronised among the South African females. / AFRIKAANSE OPSOMMING: Die vaalhaai, Galeorhinus galeus, kom wereld-wyd voor en is van groot ekonomiese belang in baie lande. Die spesie se voorplantings biologie is reeds redelik deeglik ondersoek maar intraspesifieke verskille tussen verskillende wereld populasies noodsaak die bestudering van populasies afsondelik. Daar is 70 mannetjies en 74 wyfies versamel vir hierdie studie langs die Suid Afrikaanse suid-wes kus tussen 34°8'S; 18°27'E and 34°24S; 21°25'E. Morfologiese veranderinge is beskryf en serum hormoon konsentrasies is ge-evalueer deur middel van die ELISA tegniek vir 'n amper-volledige voortplanting siklus. Mannetjies vertoon 'n jaarlikse spermatogeniese siklus met 'n piek in testosteroon konsentrasies aan die begin van spermatogenese in April-Mei. Hiema daal testosteroon vlakke tot minimum vlakke in die laat-winter, waama spermiogenese begin. Die proporsie spermiogeniese siste in die testis vermeerder tot maksimum waardes bereik word tussen Februarie en April. Paring vind hiema plaas tot omtrent Julie. Wyfies (aplasentaal vivipaar) het 'n voorgestelde driejaarlikse siklus, soortgelyk aan die Brasiliaanse & Australiese populasies maar anders as die Kalifomiese & Mediterreense populasies. Tydens die eerste jaar na bevalling vind daar nie veel voortplantings ontwikkeling plaas nie. Die daaropvolgende jaar verhoog vitellogeniese aktiwiteit in die ovarium follikels en ontwikkeling van die dopkliere en uteri. Ovulasie vind nader aan die einde van hierdie jaar plaas. Paring vind heel moontlik twee tot drie maande voor ovulasie plaas, wat noodsaak dat die wyfies sperm moet stoor in hulle dopkliere. 'n 12- 15 maande dratyd begin na ovulasie en eindig in geboorte teen die volgende somer. Testosteroon en estradiol konsentrasies fluktueer saam en speel 'n rol tydens voorbereidings vir ovulasie en dopklier ontwikkeling. Progesteroon vlakke piek twee maal gedurende die jaar, in beide onvolwasse en volwasse wyfies, maar dit kon nog nie funksioneel geassosieer word met enige voortplantings aktiwiteit of toestand nie. Die siklus is nie baie nou gesinkroniseer onder die Suid Afrikaanse wyfies nie.

The mechanisms and functions of shark grouping behaviour have received relatively little scientific attention to date. The current widespread use of social network analysis to study animal groups, in concert with rapid advances in animal tracking technology, now allows us to test specific hypotheses about how and why sharks form groups. This thesis uses replicated laboratory experiments to investigate some of the mechanisms underpinning aggregation in a model species of benthic, oviporous elasmobranch, the small spotted catshark (Scyliorhinus canicula L. 1758; Scyliorhinidae). Acoustic tracking of this species in the wild is also conducted to explore how network analyses can be adopted to study the localized movements, habitat connectivity and ranging behaviour of adult sharks. Groups of juvenile S. canicula were characterized by non-random social preferences, crucially, only when individuals were familiar with one another suggesting social recognition is important in young sharks of this species. Genetic analyses of parent and offspring DNA revealed very high levels of multiple paternity in this species, likely due to male sexual harassment and multiple mating, which leads to increased genetic diversity between juvenile sharks. Perhaps unsurprisingly, there was no evidence of kin relatedness structuring social interactions between conspecifics. Furthermore, testing the effects of environment on social behaviour provided evidence that these juveniles aggregated more in structurally complex environments than simple ones. However, at the individual level sharks showed consistency in their social network positions through time and across different habitat types. This result is indicative of personality traits in S. canicula. Using data gathered via passive acoustic telemetry of wild shark behaviour, network analysis provided a useful tool with which to quantify movement between receivers. One chapter has been dedicated to the application of these methods, highlighting a number of different analyses for predicting movement behaviour from such data. Finally, these methods were adopted to address ecological questions in this sexually segregated species. Persistent site fidelity to a localised inshore area by both male and female sharks suggested that segregation occurred at a relatively small spatial and temporal scale. Despite strong evidence of segregation, analyses of movement networks and individual co-occurrences revealed distinct periods of behavioural synchronicity during the months of March, April and May. In addition, habitat complexity appeared to be a significant driver of female behavioural strategy. Enhancing our knowledge of the social and environmental drivers of aggregation and movement in sharks is of great importance given the ecological threat facing many of our ocean’s top elasmobranch predators.

The Chandeleur Islands (Louisiana) contain nursery habitats for lemon sharks that provide abundant prey and protection from predation. Other local shark species (Atlantic sharpnose, bull, and blacktip sharks) co-occur with lemon sharks in the same region, including the nearby Biloxi Marshes. To better assess how lemon sharks use these nursery habitats, I measured diet and prey availability of young of the year and juvenile lemon sharks from 2009 to 2010. Young lemon sharks at the Chandeleur Islands have a relatively reduced diet breadth in comparison to those from nurseries in Bimini (Bahamas) and the Florida Keys. At the Chandeleur Islands, young lemon sharks appear to be opportunistically feeding on the most abundant prey items, resulting in high prey abundance and low diversity in their diet. Opportunistic feeding by young lemon sharks suggests minimal dietary overlap with other local shark species, resulting in minimal competition for resources.

The hydrodynamics of three different shark heads: Eusphyra blochii (Winghead shark), Carcharhinus acronotus (Blacknose shark) and Sphyrna tiburo (Bonnethead shark) were investigated. Force transducer measurement was used to explore how the cephalofoil (wing-shaped head) affects maneuverability and efficiency. As the dynamic behavior of maneuvering wings differs from that of the steady state motion, experiments have been conducted to simulate: 1) steady-state (no yaw motion) constant velocity swimming, 2) constant forward velocity with yawing motion of the head and 3) turning maneuvers. Different range of velocities, angle of attack, yaw frequency and yaw amplitude were tested. Drag and lift coefficients were calculated and compared. The lift coefficient of Winghead shark is much higher compared to the other sharks. The lift-to-drag ratio showed that the Winghead shark has a hydrodynamic advantage compared to Blacknose shark and Bonnethead shark. / by Julien Barousse. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Commercial longline fishing results in large amounts of incidental bycatch of elasmobranch fishes (sharks, skates, and rays). Teleost species lack electrosensory systems and development of technologies which target the ampullary organs of sharks provides an avenue to selectively deter elasmobranchs without affecting the catch rate of target teleosts. Electric field measurements and a controlled scientific longline study were conducted testing whether the lanthanide metal neodymium or zinc/graphite might reduce elasmobranch catch per unit effort (CPUE). Baited longline hooks were treated with neodymium and zinc/graphite and catch rates were compared to that of controls. Shark CPUE decreased by 60% on neodymium treated hooks and 80% on zinc/graphite treated hooks. The effectiveness of both treatments varied among species with significant reductions shown for Atlantic sharpnose sharks (Rhizoprionodon terranovae) but less dramatic differences for others. Zinc/graphite is potentially a viable tool for reduction of shark bycatch in a commercial longline fishery. / by Kieran Thomas Smith. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Resumo: No âmbito de um estudo sobre a ecologia e a pesca de tubarões costeiros no litoral centro-sul de São Paulo, foram feitas amostragens semanais junto aos desembarques da frota artesanal sediada na Praia dos Pescadores, no município de Itanhaém. Os barcos operam a uma distância de 2 a 12 milhas náuticas (20 km) da costa, em profundidades de 5 a 30 m, utilizando redes de emalhe. Entre julho de 1996 e dezembro de 2003, foram examinados 14730 exemplares, compreendendo sete famílias, nove gêneros e 18 espécies. A acumulação de espécies em função do número de amostragens apresentou tendência de estabilização a partir de 90 amostragens. Em geral, a diversidade foi menor no outono-inverno e maior na primavera-verão. A captura por unidade de esforço (CPUE) dos tubarões apresentou picos nos meses de início (janeiro e fevereiro), meio (julho e agosto) e final de ano (novembro e dezembro). Essas flutuações estiveram associadas aos padrões de recrutamento, distribuição e ocorrência das espécies mais abundantes. Cinco espécies de Carcharhiniformes utilizam o litoral centro-sul de São Paulo como área de berçário entre o inverno e verão. O tempo de permanência dos neonatos e jovens na área de estudo esteve inversamente relacionado com o tamanho de nascimento das espécies, indicando maior dependência dos filhotes menores por águas mais rasas e, supostamente mais protegidas de predadores. Foi observada uma assincronia seqüencial na atividade de parto das espécies, sugerindo que o estabelecimento de berçários coletivos aumenta as chances de competição e predação entre os filhotes. Pressões seletivas neste sentido parecem levar ao desenvolvimento de táticas reprodutivas que amenizam esses efeitos, reduzindo a mortalidade natural dos filhotes durante os primeiros meses de vida. / Abstract: Ecological aspects of the coastal sharks caught by artisanal fisheries from southeastern Brazil were studied between July 1996 and December 2003. The fishing fleet comprised 12 small motorized boats (4 - 10 m long), using monofilament gill nets with 1500 m length and stretched mesh sizes of 7, 12 and 14 cm on average. The nets are set within an area of 2 - 12 nautical miles from the shore, in waters between 5 and 30 m deep. During the study period, 14730 sharks of seven families, nine genera and 18 species were examined. In general, diversity was highest in spring-summer and lowest in autumn-winter. Catch per unit of effort (CPUE) showed peak in outset (Jan-Feb), middle (Jul- Aug) and, end (Nov-Dec) of the years. Both diversity and CPUE fluctuations were associated with recruitment, distribution and occurrence of the five most abundant species (Rhizoprionodon lalandii, R. porosus, Sphyrna lewini, Carcharhinus brevipinna and C. limbatus), that represented 96% of the total catch. These species use the study area as nursery between winter and summer with a sequence of parturition progressing from the smallest (R. lalandii, 35 cm birth size) to the largest species (C. limbatus, 70 cm birth size). Such pattern was associated with reproductive tactics that may minimize both inter-specific predation and competition among newborns, thereby reducing natural mortality during their first few months of life. / Orientador: Ivan Sazima / Coorientador: Otto Bismarck Fazzano Gadig / Banca: Ricardo Clapis Garla / Banca: Ricardo de Sousa Rosa / Banca: Marcos César de Oliveira Santos / Banca: Roberto Goitein e Otto Bismarck Fazzano Gadig / Doutor

Industrial fishing practices and market-demand for shark products (in particular meat and fins) are decimating shark populations in many parts of the world, threatening stock collapses, species extinctions and broader ecological impacts. This dissertation explores the development of the international legal regime applicable to the conservation and management of sharks, and seeks to document and provide a critical analysis of the fisheries management and conservation instruments and measures that apply or can be applied to sharks. This is followed by a review and critical analysis of the South African legal regime applicable to the conservation and management of sharks, which to the writer’s knowledge has not been clearly documented in referenced research. Both the international and South African regulatory regimes relating to the conservation and management of sharks are characterized by fragmentation, lack of co-ordination and enforcement challenges that risks duplication of effort and regulatory gaps. However, it is argued that the existing mix of hard and soft law instruments does provide a suite of regulatory options, guiding principles and frameworks which, if effectively coordinated, refined, implemented and enforced, could go a long way towards protecting sharks from overexploitation internationally and within South African waters. It is argued that the precautionary and ecosystems approaches need to applied at both a national and international level to ensure that shark are managed in an ecologically sustainable manner. Where appropriate, a moratorium (or at least a significant limitation) on the killing of sharks (through both directed and by-catch fisheries) should be imposed until such time as sufficient scientific data is available to demonstrate that shark fishing does not pose a significant risk of serious or irreversible harm. It is argued further that South Africa needs to make a serious commitment to improving shark conservation and management measures by making sufficient human and financial resources available to achieve its shark conservation and management objectives, and that the fragmented national legal regime could be enhanced and rationalised by promulgating a single shark-specific regulation that deals specifically with the conservation and management of sharks. / Thesis (LL.M.)-University of KwaZulu-Natal, Durban, 2014.

Thesis (Ph. D.)--Duke University, 2007. / Includes bibliographical references.