Siganus Javus Research Articles

RESTORASI EKOSISTEM PADANG LAMUN MELALUI TEKNOLOGI BIO-FADs TREE DENGAN BAHAN DASAR RUMPUT LAUT PADA PERIKANAN DEMERSAL

Coastal water ecosystems in general have experienced damage as a result of fishing that is not environmentally friendly. This unfriendly fishing causes the fish's feeding grounds to be damaged so that fishing activities in coastal areas need to involve fishing aids to collect fish. The fishing aids implemented are in accordance with the fishing objectives to be achieved. The implementation of fishing aids aims to attract attention and bring fish to the area where the attractor is installed, making it easier to catch. One of the fishing aids used is Biological Fish Aggregating Devices (Bio-FADs Tree) or live FADs equipped with Kappaphycus alvarezii seaweed which acts as an attractor to attract fish so they can be easily caught. This service is carried out in Mamuju waters for the purpose of catching demersal fish. The service is carried out using trap fishing equipment. The results of the service showed that the catches obtained were Pink ear emperor (Lethrinus lentjan), Redbelly yellowtail fusilier (Caesio cuning), Streaked spinefoot (Siganus javus), batik Vermiculated spinefoot (Siganus vermiculatus) and Orange-spotted spinefoot (Siganus gutattus), White-spotted spinefoot (Siganus canaliculatus), and Surf parrotfish (Scarus rivulatus). All of the catches are fish of important economic value

Trace metals accumulation in tropical fish collected from Southeast coast, Tamil Nadu, India: Implication on pollution

The present study examined the levels of accumulation pattern of seven heavy metals such as essential metals (Iron (Fe), Magnesium (Mg), Zinc (Zn), Copper (Cu)) and non-essential metals (Cadmium (Cd), Lead (Pb), Mercury (Hg)) in 13 tropical marine fishes collected from three major fish landings viz., Chennai, Nagapattinam and Tuticorin, Tamil Nadu. The overall accumulation pattern of all metals was found to be significant (P<0.05) between different species and three different landing centres. The orders of heavy metals in descending order were Mg > Fe > Zn > Cu > Hg > Pb > Cd in Chennai, followed by Mg > Fe > Zn > Hg > Pb > Cu > Cd in Nagapattinam, and Mg > Fe > Zn > Cu > Hg > Pb > Cd in Tuticorin. Bioaccumulation of metals showed preferential accumulation in muscle tissues of fish species viz., Otolithus ruber, Siganus javus, Atule mate, Sardinella gibbosa, Nemipterus japonicus, Lutjanus fulviflamma, Rastrelliger kanagurta, Gerres filamentosus, Sphyraena obtusata, Selar crumenophthalmus, Upeneus moluccensis, Plicofollis dussumieri and Sillago sihama. The metal concentrations were found dependent on species-specific, behaviour of feeding, pattern of swimming and genetic tendency or other factors such as age and geographical distribution. The metal concentration varied from the fish species. Principal component was analysed and found that heavy metal concentrations detected in the study do not pose a major risk to human being. The present work suggests to continuously monitor the polluted areas for a long-term basis, as the fishes show a tendency of accumulating even non-essential metals from polluted waters.

Novel Interaction between a Rabbitfish and Black Corals

Herbivorous fishes play important functional roles in coral reef ecosystems, and their influence on mediating competitive dynamics between corals and macroalgae is well studied. Nonetheless, direct interactions between herbivorous fishes and corals may also be relevant, although these are less studied. Here, we describe a series of observations of schools of the herbivorous streaked rabbitfish (Siganus javus) nibbling on black corals (order Antipatharia) at the SS Yongala wreck, within the Great Barrier Reef Marine Park. We provide a hypothesis that may explain this behaviour, which, if confirmed, would represent a mechanism influencing the health of the corals. Moreover, this interaction extends the typical coral–algae competition for space paradigm and furthers knowledge of complex relationships between coral reef organisms.

Diversity, carbon stock and associated biota of seagrass beds in Central Tapanuli District, North Sumatra, Indonesia

Abstract. Maulita M, Nugraha E, Suharti R, Tanjung NW, Sayuti M, Mulyono M, Mantani S, Setiarto RHB. 2023. Diversity, carbon stock and associated biota of seagrass beds in Central Tapanuli District, North Sumatra, Indonesia. Biodiversitas 24: 2080-2087. Various human activities emit carbon dioxide which drives global warming and climate change. Seagrass ecosystems can absorb and store enormous quantities of carbon, hence reducing carbon emissions. This research aimed to assess the diversity, vegetation cover, carbon stock and associated biota of seagrass beds in Central Tapanuli District, North Sumatra, Indonesia. Purposive sampling method was employed with data collection used the line transect quadrant method. Carbon stock was measured using the loss of ignition method. There were four species of seagrass in the studied area, namely Enhalus acoroides (L.f.) Royle, Thalassia hemprichii (Ehrenb. ex Solms) Asch., Cymodocea rotundata Asch. &amp; Schweinf. and Halodule uninervis (Forssk.) Boiss. with a density ranging from 23-164 stands/m2. Seagrass cover ranged from 3.87%-34.37%. Associated biota (fish and crustaceans) at each observation station were Siganus javus Linnaeus 1766, Siganus canaliculatus Park 1797, Siganus vermiculatus Valenciennes 1835, Colomesus psittacus Bloch &amp; Schneider 1801, Epinephelus fuscoguttatus Forsskål 1775, Terapon jarbua Forsskål 1775, Ambassis dussumieri Cuvier 1828, Cryptocentrus leptocephalus Bleeker 1876, Leiognathus robustus Sparks &amp; Dunlap 2004, Portunus armatus A.Milne-Edwards 1861, Rhinolambrus pelagicus Rüppell 1830 and Hippolyte obliquimanus Dana 1852. The total carbon stock of the top substrate (leaves) was 12.8 tons, while carbon bottom substrate (rhizomes and roots) was 12.9 tons, resulting in a total carbon stock of 25.7 tons. The analysis of water quality parameters indicated that the studied area had suitable environmental conditions for seagrass growth. The results of this study add new information regarding seagrass ecology of the western region of Indonesia, especially Sumatra.

Concentrations of trace metals in Siganus javus captured in Negombo estuary, Sri Lanka: Human health risk assessment through dietary exposure

Concentrations of aluminium, cadmium, chromium, lead, nickel and zinc in muscle and liver of a marine fish in Indo-Pacific region, Siganus javus captured in Negombo estuary were evaluated and potential human health risks associated with dietary exposure were assessed. Of the six metals analyzed, zinc was the most abundant metal in both tissues. No significant differences were found between muscle and liver with respect to cadmium and lead concentrations whereas concentrations of other metals were higher in liver compared to muscle. In human health perspective, estimated target hazard quotients for cadmium and lead were greater than the threshold of one indicating potential non-cancer health risks to heavy consumers. Estimated excess cancer risk of cadmium indicate carcinogenic health risks associated with their consumption even at moderate meal frequencies. The results revealed that consumption of S. javus from the estuary needs to be limited concerning non-cancer and cancer risks to human health.

Live Jellyfish-baited Small-scale Traditional Trap Fishery Operated off the Eastern Coast of Sri Lanka

The jellyfish-baited trap fishery was studied at four fishing grounds off the eastern coast of Sri Lanka throughout the entire fishing season (February and March) in three consecutive years, from 2017 to 2019, due to its uniqueness of export-oriented small-scale fishery. The composition of catch and their respective stomach content analysis revealed that the highly expensive Malabar groupers, which are predominantly targeted for export markets get attracted to traps as the secondary catch because they predate on the primary catch, e.g ., filefishes, rabbitfishes, surgeonfishes and triggerfishes, and the bycatch, i.e ., angelfishes and butterflyfishes. The varieties of primary catch are attracted to the jellyfish-bait. Among the 24 species of fishes caught, medusivorous Siganus javus had the highest abundance (24%), followed by Acanthurus mata (21%). Family-wise, the maximum contribution to the total catch was by Siganidae (56%), followed by Acanthuridae (34%). The average CPUE (kg three-man group-1 boat-1 day-1) ± SD of primary, secondary and by-catch during the fishing season was 87.0 ± 18.4 kg (~80%), 15.1 ± 3.4 kg (~14%) and 6.3 ± 1.4 kg (~6%) respectively, while the average total catch per trap was 7.2 ± 1.4 kg. The results of this study are important for utilizing the commonly available jellyfish bait to expand this trap fishery as well as to adapt the strategies for similar fisheries.

First hatchery bred streaked spinefoot rabbitfish (Siganus javus) in Sabah, Malaysia

The present study aims to expand the market potential of the streaked spinefoot rabbitfish (Siganus javus) in Malaysia and provide consumers more choices of affordable protein source from aquaculture. Spawning hehavior of S.javus was recorded in a week after the new moon in October 2019 and January 2020. Spawning occurred between midnight and early morning, and the eggs hatched about 16 to 18 hours later. Throughout the incubation and larvae rearing period, water temperature was maintained at 30 to 31 °C. Water salinity, pH and DO were 31 to 33 ppt, 7.8 to 8, and 5 to 7 mg/l, respectively. Eggs diameter ranged from 0.550 to 0.603 mm. At 1 day after hatched (d AH), eyes of the larvae were formed but unpigmented and mouth structure was not developed. At 2 d AH, the pigmentation of eyes darkened, digestive tract formed, and anus and mouth opened. At 3 d AH, the lower jaw began to show movement, indicating that the ability of larvae to indulge in feeding. The buds of dorsal and ventral fins started to develop and elongate from 9 d AH and were covered with melanophores. At 25 d AH, the body of the larvae turned brownish and abdominal cavity was deeply pigmented, indicating the onset of metamorphosis. By the age of 30 d AH, the larvae completed development into juvenile stage. At 270 d AH, the juvenile reached maximum size of 21 cm in total length. This study was the first successful attempt at naturally spawning and hatchery rearing of S. javus into juvenile stage in the country. The development of a complete larval rearing protocol for S. javus could provide information of practical importance in hatchery breeding of other rabbitfish species.

The Use of Hematological and Histopathological Biomarkers to Assess the Health of Aquatic Ecosystems in Koh Sichang, Thailand

Abstract Koh Sichang area in Thailand is a sink for a wide variety of contaminants such as heavily polluted water from industry and oil spills. This situation may affect the health status of fish living in the area, but such information remains scarce. In this study, we evaluated the health status of java rabbitfish Siganus javus, an important marine fish in Koh Sichang, using hematological and histopathological biomarkers. All fish samples were collected from the Koh Sichang area during December 2017 and January 2018. Although the salinity, pH, and dissolved oxygen levels at sampling points were all within the normal range, abnormal nuclei were observed in erythrocytes (up to ~6% of all erythrocytes) and in some leucocytes (neutrophil, lymphocyte and monocyte). Visceral organs (gill, kidney and liver) were apparently normal in terms of gross morphology, but a wide variety of the histopathological alterations were found at the microscopic level: epithelial hyperplasia and aneurysm in gills; blood congestion and melanomacrophage centers (MMCs) in the liver; renal degeneration, granuloma and MMCs together with unidentified parasites in kidney. Calculation of semi-quantitative parameters [histological alteration index (HAI) and the average value of alteration (AVA)] demonstrated the highest frequency of histopathological alterations in kidney, suggesting that kidney is a sensitive organ. Overall, our observations suggest that S. javus in Koh Sichang is under the pathological state and warrants conservation efforts. Keywords: Erythrocytes, Fish Health, Hematology, Histopathology, Kidney

Fear effects and group size interact to shape herbivory on coral reefs

AbstractFear of predators (‘fear effects’) is an important determinant of foraging decisions by consumers across a range of ecosystems. Group size is one of the main behavioural mechanisms for mitigating fear effects while also providing foraging benefits to group members. Within coral reef ecosystems, fear effects have been shown to influence the feeding rates of herbivorous fishes, a key functional group that prevents macroalgal overgrowth. Yet, how fear effects and group size interact to shape macroalgal removal on coral reefs remains unclear.Here, we conducted field‐based experiments using models of a common piscivorous fish, the leopard coral grouperPlectropomus leopardusand a series of macroalgalSargassum ilicifoliumassays positioned at increasing distances from the models (1, 2, 3 and 4 m) on two coral reefs in Singapore to investigate how acute fear effects shape the intensity of herbivory, and whether these effects were influenced by variation in the group size of herbivorous fishes feeding on the assays.We found acute fear effects strongly influenced the foraging behaviour of herbivorous fishes over small spatial scales. Rates ofSargassumbiomass removal, feeding rates and the total number of individual feeding events were all lower near the predator model. These effects dissipated rapidly with increasing distance from the predator model and were undetectable at a distance of 4 m. We also found generally larger group sizes of herbivorous fishes further from the predator model, presumably reflecting decreased risk. Furthermore, the number of individual bites/event increased significantly with increasing group size for two common browsing fishes,Siganus virgatusandSiganus javus.Our findings highlight that acute fear effects influence the distribution and intensity of herbivory over small spatial scales. Fear effects also interacted with herbivore group size resulting in changes in the number of individual feeding events and bite rates that collectively shape the realized ecosystem function of macroalgal removal on coral reefs. Group size is an important context‐dependent factor that should be considered when examining fear effects on coral reefs.A freePlain Language Summarycan be found within the Supporting Information of this article.

Short term culture of wild caught juvenile rabbit fishes (Siganus javus) in open sea cages at Palk Bay

Objectives: The main objective of the study was to collect and rear the unmarketable, small sized S.javus which is mostly rejected by the traditional fisherman. During fishing activities, under sized S.javus ranging in sizes from 25 to 40 kg (&lt; 30-40 % of total catch/day) is being captured. Due to very low marketable value these small fishes (&lt;250 g) get rejected. Therefore, we utilized this as an economically viable option for utilization as seeds for rearing until they reach the necessary marketable size. Methods: Undersized juveniles (12-16 cm, 40 -55 g) were collected from nearby Olaikuda village,Rameshwaram using traditional traps made using bamboo and odai tree bark (Acacia planifrons). The collected juveniles were stocked in sea cages and fed with locally formulated plant based feed containing 28-32 % crude protein. Findings: Harvesting was successfully done after 140 days with 90 % survival. The average growth rate achieved was 2.5 g /day with FCR of 2.01. This resulted in an average harvest size of 400 g/fish from its initial stoking size of 50 g with an attracted market value of Rs. 150/kg. Novelty: Till date, no attempts were made to commercialize such harvesting techniques for the species Siganus javus in pilot scale in India (Except James, 1984). Keywords: Rabbit fish; Siganus javus; sea cage culture; rabbit fish culture; Siganidae

Fish Assemblages in Iraqi Marine Waters, North West The Arabian Gulf

The composition of fish assemblages in Iraqi marine water was assessed. 91 species belonging to 71 genes and 47 families of Osteichthyes and 13 species of Conderchthyes were collected during the study period from January to December 2018, using trawl net fishing. Three stations were selected, where two new species (Siganus javus and Gobiopsis sp.) and reclassification of Torpedo panthera where identified and two species of freshwater fish (Oreochromis niloticus and Oreochromis aureus) were first recorded in marine waters. The highest numbers of species were 32 and 42 for the first and second stations, respectively, recorded in October , while 55 species were recorded in the third station during August. Leiognathus bindus was the dominant species in the first and second stations, while Ilisha compressa dominated the third station. Carangidae and Sciaenidae were the dominant families in number of species (7 and 5, respectively), whereas 4 species were recorded for Clupeidae, Sparidae, Mugilidae and Gobidiae.

Heavy metals content (Hg, Cd, Pb, and Cu) in streaked spinefoot Siganus javus (Linnaeus, 1766) in Bojonegara Waters, Banten Bay, Indonesia

Anthropogenic activities contribute to heavy metals so that their concentration in the waters increases and causes accumulation, especially in streaked spinefoot. This study aims to estimate the level accumulation of (Hg, Cd, Pb, and Cu) heavy metals contained in streaked spinefoot (Siganus javus) meat in Bojonegara waters, Banten Bay, Indonesia. A sampling of 30 to 50 grams of fish meat is carried out every month from August to October 2020 and heavy metals analysis in streaked spinefoot meat was carried out in February 2021 using atomic absorption spectrophotometry (AAS). The (Hg, Cd, and Pb) heavy metals contained in the streaked spinefoot meat were undetected by the AAS, while the content of heavy metal Cu on small fish is 0.348 to 1.530 mg kg-1, and large fish is less than 0.015 mg kg-1 to 5.390 mg kg-1. Bioaccumulation Cu metal in small and large streaked spinefoot included low to high accumulation, while it was low for other types of metal. The safe limit for consumption of streaked spinefoot meat for adults (50 kg) is 32.468 kg of meat/week, while for children (15 kg), it is 9.740 kg of meat/week.

The Streamlined Rabbitfish Siganus argenteus (Quoy &amp; Gaimard, 1825) in the Mediterranean Sea

The Mediterranean native biota is increasingly threatened by the influx of alien species. More than 100 non-native fishes have entered so far the Mediterranean, the majority of which presumably originated in the Red Sea. Among them, two species of the family Siganidae, namely Siganus luridus and Siganus rivulatus, are now widespread in the eastern Mediterranean Sea and already reached the central parts of the basin. Three further Siganus taxa, namely Siganus fuscescens, Siganus javus, and Siganus virgatus, have also been recorded from the Mediterranean basin, although their records are based on single specimens. We report the first sighting in the Mediterranean Sea of a single specimen of an additional rabbitfish, namely Siganus argenteus. There are no certainties regarding the possible pathway of arrival of this species in Libya; however, Lessepsian migration or shipping constitute the most probable ones.

First Record of Streaked Rabbitfish Siganus Javus (L., 1766) from the Iraqi Marine Waters, with Re Description of White-Spotted Rabbitfish Siganus Canaliculatus (Park, 1797)

Two Siganid fishes were described in the current study, the first one is Siganus javus (Linnaeus, 1766) as a new record and the other Siganus canaliculatus (Park, 1797), which was collected from the Iraqi marine waters. The samples were collected during December 2018. Streaked rabbitfish S. javus is diagnosed by a deep body, 54.01% in standard length, depth of caudal peduncle, 7.27%, total gill rakers 19 and silvery blue undulating lines on mid and lower sides of the body. Whereas the body depth of White-spotted rabbitfish S. canaliculatus was 39.08-42.66%, Caudal peduncle depth ranged from 5.21 to 5.66%, total gill rakers ranged from 22 to 24 and it is distinguished by a numerous pearly blue to whitish spots on the nape and trunk.

PERBANDINGAN HASIL TANGKAPAN BUBU PADA JENIS TERUMBU BUATAN BAN DAN BAMBU DI PERAIRAN DESA TOISAPU KECAMATAN BAGUALA AMBON

Information about material kinds of artificial reef which effective for marine organism habitat is rare. Based on this fenomena, It is important to conduct a study about bamboo and tire artificial reef. The objective of this study is to find out a catch comparison and species compotition of pot catch on bamboo and tire artificial reef. Alternatif a widely used materials are bamboo and tire with consideration easy to obtain and economis. The result of this study show that the total catch during the study was 170 fishes from 8 species dominated by Siganus javus, Seranidae sp and Carangidae sp. The total catch of the Tire artificial reef was 87 fishes including 48,19 % Siganus sp, 23,53% Seranidae sp and 10,06 % Lethrinidae sp where as Bamboo artificial reef was 83 fishes including 33,34 % Siganus sps,26,3% Seranidae sp and 14,26 % Carangidae sp . The result showed that catch of bamboo artificial reef was significantly difference from the catch of tire artificial reef where the catch of tire artificial reef was higher than that catch of bamboo artificial reef.

Morphometric and molecular characterisation of Tenuiproboscis keralensis n. sp. infecting marine and brackish water fishes from the south-west coast of India with a note on morphological plasticity.

A new species of acanthocephalan infecting marine and brackish water fishes from the south-west coast of India is described. The parasite belongs to the genus Tenuiproboscis, and the fish hosts include Lutjanus argentimaculatus, L. ehrenbergii, Siganus javus, Epinephelus malabaricus, E. coioides, Scatophagus argus, Parascolopsis aspinosa, Caranx ignobilis, Gerres filamentosus and Lates calcarifer. The parasite inhabits mid- and hindgut regions and is characterised by an elongated, cylindrical, bulbous and posteriorly tapering metasoma and a claviform proboscis having 14-15 rows of 14-15 hooks each. Females larger than males, measured 3898.16-10,318.00μm (6430.00±1417.30) in length and 458.93-1435.68μm (929.81±250.39) in width. Males measured 3234.89-8644.20μm (5729.50±1176.60) in length and 388.30-1584.61μm (795.88±184.12) in width. Parasites recovered from different host species showed morphological/morphometric variations. However, principal component analysis (PCA) revealed significant overlapping of characters indicating their similarities. Proboscis profiling based on variations in size and position of hooks also yielded similar results. Further, in molecular phylogenetic analysis, parasites from different fish hosts formed a monophyletic clade with strong bootstrap support, again indicating their conspecific nature. These morphological/morphometric variations can be ascribed to differences in host species. Morphology and morphometrics in combination with PCA, proboscis profiling and molecular analysis suggest the present acanthocephalan parasite is different from other described species of Tenuiproboscis. Hence, it is considered as a new species and named T. keralensis n. sp. Prevalence, intensity and abundance of the parasite in different hosts are also discussed.

Stable isotope analysis suggests the existence of multiple populations of streaked spinefoot (Siganus javus L.) in Bandon Bay, Southern Thailand

The stock unit used in fisheries resource assessment and management is generally based on the morphological and genetic characteristics of a particular population or species to avert problems caused by the treatment of multiple populations as one stock, which can lead to the overestimation of population sizes and genetic pollution. Furthermore, since the linkage of microhabitats is an important factor affecting the reproduction of marine organisms in coastal areas, an understanding of the food web in each microhabitat is essential to establish sustainable fisheries management practices. We investigated spatial variations in the food sources and feeding habits of immature stage of Siganus javus using genetic population analyses and stable isotope analyses (δ13C and δ15N). These species are commonly harvested by small-scale fisheries, and it inhabits Bandon Bay in the Surat Thani Province of Southern Thailand. Genetic variation within sampling sites was greater than that between sites. The δ13C values of S. javus differed between sites, which suggest that the different ecological habitats exhibit different rates and patterns of carbon flow even among sites located in the same bay. Our results suggest that studies combining genetic population analyses and stable isotope analyses are required to confirm the delineation of fine-scale management units intended for the development of coastal fishery resources.

Tidal, diel and lunar patterns in intertidal and subtidal mangrove creek fish assemblages from southwest Thailand

Knowledge about short-term assembly patterns and connectivity in estuarine mangrove ichthyofauna from the Indo-West Pacific region is scant. We assessed tidal and diel dynamics of intertidal and subtidal fish assemblages in the mangrove forest of Sikao Creek, southwest (Andaman coast) Thailand. Over three lunar cycles, two intertidal creeks were blocked at high water according to the interaction of tidal and diel cycles; the adjacent subtidal area was seined at low waters. A total of 18,033 individuals (93 species, 36 families) were caught. Catch mass and abundances were dominated by small-sized fishes (intertidal creeks: Apogon hyalosoma, Ambassis interrupta, Ambassis vachellii; subtidal area: A. vachellii, Neostethus lankesteri, Oryzias javanicus, Siganus javus). Of 45 intertidal species, 78 % were also caught in the subtidal, suggesting close connectivity between the two habitat types. Overall intertidal fish biomass (0.3 g m−2) and density (0.03 fish m−2) were relatively low. Specific combinations of tidal magnitude and diel cycle explained recurring changes in intertidal fish assemblage structures, clearly observed at the species level, in the number of species, diversity, evenness and biomass. This pattern was strongly driven by new moon-night abundance maxima of dominant A. vachellii, which also displayed fullest stomachs at this lunar-diel cycle interaction. We suggest that estuarine mangrove fish studies of the Andaman Sea region may suffer significant bias when the importance of tidal-lunar and diel cycle interactions are not considered because the role of Ambassidae will be strongly underestimated.

Experimental farming of Kappaphycus alvarezii (Doty) Doty with income estimates at different sites in the Mandapam region, Palk Bay, southeast coast of India

The cultivation of Kappaphycus alvarezii, a kappa carrageenan producing red seaweed, was done for 1 year from April 2012 to March 2013 in subtropical waters of Indian Peninsula at three different sites (Mangadu in Rameswaram Island, Munaikadu and Vedalai—on main land coast) on Palk Bay side of Bay of Bengal of Rameswaram–Mandapam region of southeast coast of India. These experiments were carried out to confirm the results obtained in an earlier study (April 2011 to March 2012) at more or less the same sites—one is different (Mangadu) and two are the same (Munaikadu and Vedalai). The maximum crop yields of 326.55 ± 10.23 and 316.65 ± 15.13 kg FW raft−1 were obtained in October 2012 at Mangadu and Munaikadu, respectively, and 308.40 ± 8.89 kg FW raft−1 in March 2013 at Vedalai. Similarly the maximum daily growth rates (DGRs) of 3.76 ± 0.07 and 3.69 ± 0.11 % were found in October 2012 at Mangadu and Munaikadu, and 3.64 ± 0.06 % was obtained in March 2013 at Vedalai. A significant negative correlation between DGR and seawater temperature at Mangadu (r = −0.604) and Munaikadu (r = −0.700) was found (at 0.05 level). Further, a significant positive correlation was seen (at 0.05 level) between nitrite and phosphate at Mangadu (r = +0.613) and Vedalai (r = +0.599). However, salinity and seawater temperature were significantly positively correlated (r = +0.693) at Munaikadu (at 0.05 level). ANOVA showed that the growth rates among these three sites were found to be statistically insignificant. Tip grazing by Siganus javus and Diodon holocanthus during the monsoon period (October 2012 to January 2013) was observed. Seasonal epiphytes Lyngbya majuscula and Cladophora facsicularis were the main problematic epiphytes from April to June. Net income would be Rs15,000 to Rs16,000 (US$250–US$265) per month, and if the cultivation is taken up in earnest perspective, the farmers would improve their living standards.

Community structure and coral status across reef fishing intensity gradients in Palk Bay reef, southeast coast of India.

Coral reef fishes are exploited without the knowledge of their sustainability and their possible effect in altering the community structure of a coral reef ecosystem. Alteration of the community structure could cause a decline in the health of coral reefs and its services. We documented the coral community structure, status of live corals and reef fish assemblages in Palk Bay at the reef fishing hotspots and its nearby reef area with minimum fishing pressure and compared it with a control reef area where reef fishing was banned for more than two decades. The comparison was based on the percent cover of different forms of live corals, their diversity and the density and diversity of reef fishes. The reef fish stock in the reef fishing hotspots and its neighbouring reef was lower by 61 and 38%, respectively compared to the control reef. The herbivore fish Scarus ghobban and Siganus javus were exploited at a rate of 250 and 105 kg month(-1) fishermen(-1), respectively, relatively high comparing the small reef area. Live and dead corals colonized by turf algae were predominant in both the reef fishing hotspots and its nearby coral ecosystems. The percent cover of healthy live corals and live corals colonized by turf algae was <10 and >80%, respectively, in the intensively fished coral ecosystems. The corals were less diverse and the massive Porites and Favia colonies were abundant in the intensive reef fishing sites. Results of this study suggest that the impact of reef fish exploitation was not solely restricted to the intensively fished reefs, but also to the nearby reefs which play a critical role in the resilience of degraded reef ecosystems.