Edwin Mark Grandcourt

The bio-economic impact of mass coral mortality on the coastal reef fisheries of the Seychelles

Abstract Data collected through a stratified catch and effort survey were used to assess the impact of the 1998 mass coral bleaching event on socio-economic and biological indicators for the coastal reef fisheries of the Seychelles. There was a significant reduction in the abundance index and monthly yields per square kilometre for representatives of the family Siganidae following 1998. However, this was not associated with the bleaching event and conformed with the declining trend prior to the impact. Abundance indices and yields per square kilometre did not change significantly for the primary target families of the handline fisheries (Lutjanidae, Serranidae, Lethrinidae and Carangidae). Declining trends in abundance indices and yields for Octopodidae reversed after 1998, although the phenomena could not be independently linked to coral bleaching. Whilst critical resource based management issues are identified for the demersal handline fishery, the results suggest that there were no negative short-term bio-economic impacts on Seychelles coastal reef fisheries associated with mass coral mortality.

Reef Fish and Fisheries in the Gulf

The waters of the Gulf are characterized by extreme temperature (11.5–36°C) and salinity (37–50‰) ranges which are likely to at least periodically approach or exceed the tolerance limits of many reef fish species (Coles 1988; Coles and Tarr 1990). The narrow Strait of Hormuz constrains the influx of larvae from adjacent seas which also limits species diversity. Whilst the Gulf is a relatively young sea that originated about 16,000 BP, the sea surface did not reach its current level until around 6,000 BP during the Holocene (Sheppard et al. 1992). The present day fish fauna was thus established by the penetration of species from the Indian Ocean through the Gulf of Oman and Strait of Hormuz (Beech 2004). Its small size, limited habitat types and restricted depth also constrain faunal diversity, which is particularly apparent among the families of reef fishes (Randall 1995; Bishop 2003). Consequently, many major shallow water taxonomic groups that are prevalent at similar latitudes throughout the Indo-Pacific and adjacent waters are completely lacking in the area and there are few endemics, with only 16 species of fishes known to occur uniquely within the Gulf (Coles and Tarr 1990; Randall 1995; Carpenter et al. 1997).

Reproductive biology and implications for management of the orange-spotted grouper Epinephelus coioides in the southern Arabian Gulf

The reproductive biology of Epinephelus coioides was determined from the examination of 1455 individuals collected between July 2005 and June 2007 in the southern Arabian Gulf. Histological preparations of gonads indicated that males were either derived from a juvenile phase or the transition of postspawning females, confirming a diandric protogynous sexual pattern. The spawning season was well defined, occurring once a year during April and early May. Peaks in spawning occurred after the full and new moons and was completed within a single lunar cycle. The presence of mature males over the entire size and age range and the absence of inactive mature females during the spawning season suggested that the population was not constrained by sperm limitation. While specimens undergoing sexual transition were only observed in size and age ranges of 335-685 mm total length (L(T)) and 5-6 years, patterns in the proportion of males in size and age classes suggested that sex change occurred at a relatively constant rate after female maturation up to the maximum size (1002 mm L(T)) and age (11 years). Relationships between reproductive output and capacity with size and age indicated that conventional regulations that equate the mean size at first capture to sexual maturation are unsuitable for the management of E. coioides. The maximum age, small size and young age at sexual maturation (L(min)= 320 mm L(T), 2 years, for females and 242 mm L(T), 1 year, for males) conflict with the general pattern for large epinepheline groupers and may be a direct result of the intensive demersal fishery in the southern Arabian Gulf.

Comparative biology of tropical Lethrinus species (Lethrinidae): challenges for multi‐species management

Life-history characteristics of six tropical Lethrinus species sampled from the Great Barrier Reef World Heritage Area were compared. Two species groups were identified based on fork length (LF ): large species with maximum LF > 640 mm (longface emperor Lethrinus olivaceus, yellowlip emperor Lethrinus xanthochilus and spangled emperor Lethrinus nebulosus) and small species with maximum LF < 480 mm (Pacific yellowtail emperor Lethrinus atkinsoni, pink ear emperor Lethrinus lentjan and ornate emperor Lethrinus ornatus). Lifespan was not correlated with LF . Early growth for all species was rapid and similar during the first few years of life, but coefficients of the von Bertalanffy growth function varied considerably among species. Growth also differed between sexes for L. atkinsoni. Reproductive characteristics varied among species, with peak periods of spawning occurring in November to December for L. atkinsoni, July to August for L. nebulous, September to October for L. olivaceus and a protracted season for L. lentjan, although fewer samples were available for the last two species. Sex-specific LF and age distributions and gonad histology of L. lentjan were suggestive of a functional protogynous reproductive pattern, as observed in other lethrinids. Gonad histology indicated non-functional protogynous hermaphroditism for L. atkinsoni and L. nebulosus. The diversity of life histories among these closely related species emphasizes the difficulty in devising single management strategies appropriate for multi-species fisheries and illustrates the importance of understanding species-specific life histories to infer responses to exploitation.

Coral Bleaching and Mortality Thresholds in the SE Gulf: Highest in the World

Bleaching is a stress reaction in corals, during which the symbiosis between corals and the algae (zooxanthellae) living in the coral cells breaks down. As a result, zooxanthellae are expelled, and the coral appears pale or even white (Fig. 6.1; Baker et al. 2008). The link between environmental variables and coral bleaching has been well-established in a variety of studies and synthesized in several places (Phinney et al. 2006; Baker et al. 2008; van Oppen and Lough 2009). Large-scale and region-wide bleaching events, such as occur in the Gulf, have been clearly linked to unusually high temperatures and the accumulation of heat stress in corals. Other drivers, such as UV and water acidity can have compounding effects (Baker et al. 2008) and bleaching can also be caused by these factors alone, or other local drivers such as unusually cold temperatures (Saxby et al. 2003; Lajeunesse et al. 2007). However, it is heat stress that has been demonstrated as the most reliable predictor and defined time-integrated bleaching thresholds exist for various regions of the Indo-Pacific and the Caribbean (Berkelmans 2002a, b; Manzello et al. 2007; Berkelmans 2009).

Reproductive biology and implications for management of the spangled emperor Lethrinus nebulosus in the southern Arabian Gulf

The reproductive biology of the spangled emperor Lethrinus nebulosus in the southern Arabian Gulf was determined from the examination of 781 individuals collected between September 2008 and August 2009. There was no histological evidence of adult sex change, and sex ratios did not differ significantly from unity across all size and age classes. Testes had an ovarian structure and a remnant lumen which was not used for sperm transport; furthermore, residual oocytes were observed in the testes of some immature, resting and developing males. A dramatic change in the sex ratio of the smallest and youngest size and age classes suggested that juvenile female to male sex change occurred between 21·0 cm fork length (L(F)) and 24·0 cm L(F) at 1 year of age. The combination of histological evidence with the sexual composition of the size and age structures suggests a non-functional protogynous hermaphroditic sexual pattern, which is analogous to functional gonochorism. The spawning season was well defined, occurring once a year during March, April and early May. Peaks in spawning occurred after full moons, there was a cessation in spawning activity after new moons and spawning was completed within three lunar cycles. The distribution of males over the entire size and age ranges and the absence of inactive mature females during the spawning season suggested that the population was not constrained by sperm limitation. Size-specific and age-specific reproductive potential indicated that conventional regulations that equate the mean size at first capture to sexual maturation are unsuitable for the management of L. nebulosus. The maximum recorded age (11 years), small mean size and young age at sexual maturation (L(m50) = 26·7 cm L(F), 2·1 years, for females and 19·4 cm L(F), 0·5 years, for males) may be a direct result of intensive demersal fishing in the southern Arabian Gulf.

Reproductive biology and implications for management of the painted sweetlips Diagramma pictum in the southern Arabian Gulf

The reproductive biology of the painted sweetlips Diagramma pictum was determined from 487 individuals collected between January and December 2010 in the southern Arabian Gulf. There was no evidence of sex change and the combination of histological results with the sex composition of the size and age structures indicated a gonochoristic sexual pattern. There were peaks in gonado-somatic indices for females in March and October with spawning occurring during two seasons (April to May and November). The mean size and age at sexual maturity (L(m50) and A(m50) ) were 35·7 cm fork length (L(F) ) and 2·9 years for females and 26·7 cm L(F) and 0·5 years for males. The maximum recorded age (11 years) and small mean size and young age at sexual maturity for males may be a direct result of intensive demersal fishing in the southern Arabian Gulf. There was an exponential increase in the cumulative reproductive potential with size and a linear increase with age for both sexes. The mean L(F) (L(c50) ) at which D. pictum became vulnerable to capture was 33·3 cm, which corresponded to only 3 and 7% of the cumulative reproductive potential of males and females, respectively. Size-specific and age-specific reproductive potential indicated that conventional regulations that equate the mean size at first capture to sexual maturation are unsuitable for the management of D. pictum.

Low abundance of sharks and rays in baited remote underwater video surveys in the Arabian Gulf

Data on the diversity and relative abundance of elasmobranchs (sharks and rays) in the Arabian Gulf have been limited to fishery-dependent monitoring of landing sites. Understanding the diversity and abundance of sharks and rays is, however, crucial to inform policy and management plans. Baited Remote Underwater Video Surveys (BRUVS) were conducted in 2015–2016 across the United Arab Emirates Arabian Gulf waters encompassing a range of depths and habitat types. Data from 278 BRUVS (757 hours soak time) were analysed to gather information on diversity, relative abundance, species distribution, and habitat associations. Surveys recorded 213 individuals from 20 species of sharks and rays at 129 stations. The frequency of occurrence of species usually discarded by fishers such as the Arabian carpetshark (Chiloscyllium arabicum) and stingrays (Himantura spp.) was high, accounting for 60.5% of observed elasmobranchs. Despite the large survey area covered and extensive sampling effort, the relative abundance of sharks and rays was low at 0.28 elasmobranchs per hour, 0.13 sharks per hour, and 0.15 rays per hour. This CPUE was reduced to one of lowest recorded abundance on BRUVS from around the world when removing the two discarded species from the analysis (0.11 elasmobranchs per hour). These results likely reflect the intense fishing pressure and habitat loss contributing to population declines of many elasmobranchs in the Arabian Gulf. Findings provide a baseline for future work and can support the design of conservation strategies for sharks and rays in the UAE.