Coastal tourism is increasingly recognized as a vital component of the global 'blue economy', offering a critical pathway for traditional fishing communities to diversify their livelihoods amid mounting economic and environmental pressures. To understand this dynamic, this study investigates the occupational transition of 120 coastal fisherfolk into the tourism sector across two states in India. Analyzing socio-economic profiles and transition patterns, the research highlights a significant occupational shift, with 85.8% of respondents now identifying tourism as their primary income source. Demographically, the participants are predominantly middle-aged males with low educational attainment and modest living conditions. Fisherfolk strongly favor tourism over traditional fishing, citing lower physical strain, reduced risk, and more stable earnings. Consequently, this transition has led to a marked reduction in fishing labor hours and a significant income boost, with median annual tourism earnings reaching ₹252,000 (~USD 2610). Furthermore, data models reveal that a willingness to step away from traditional fishing is the strongest predictor of transition readiness. Despite these positive economic outcomes, the occupational shift is hindered by several major constraints. Disruptions from the COVID-19 pandemic, high initial investments, strong competition from established operators, poor infrastructure, and adverse weather conditions remain significant challenges. Ultimately, while tourism is increasingly central to diversifying coastal livelihoods and reducing heavy physical labor, ensuring its sustainability requires targeted interventions. Stronger institutional support, comprehensive skill development, and accessible financial mechanisms are essential to secure equitable, long-term benefits for these coastal communities.

The size selectivity of experimental longlines for two commercially important grouper species viz., Brown lined grouper, Epinephelus undulosus and Malabar grouper, E. malabaricus was investigated in the Gulf of Mannar, southeast coast of India. J-type hooks of three different sizes (hook no. #12, #9 and #6) were evaluated during experimental longline trials conducted between February 2020 and January 2022 in fishing grounds of 20 m to 30 m depth. Eight different models namely, Normal location, Normal scale, Lognormal, Gamma, Logistic, Richards, Binormal and Bilognormal were fitted using the SELECT method. Model selection based on Akaike’s Information Criterion (AIC) indicated that the lognormal model provided the best fit for E. malabaricus, while the binormal model best described selectivity for E. undulosus. The estimated mean lengths increased consistently with hook size, indicating a shift towards larger individuals with increasing hook size. Comparison of estimated mean lengths with length at first maturity revealed a substantial reduction in the probability of capturing immature fish with larger hooks. These results suggest that the use of larger hook sizes can reduce the capture of undersized individuals without compromising catch, thereby improving both selectivity and sustainability of grouper fisheries in the Gulf of Mannar.

Size selectivity of hooks used in artisanal trolling lines were examined for two commercially important species, Scomberomorus commerson and Thunnus albacares, in the Gulf of Mannar region (GoM). Catch data were collected at fortnightly intervals between September 2024 and August 2025 from trolling lines fitted with three ‘J’ hook sizes (#5, #6, and #7). Selectivity parameters were estimated using eight distinct models - normal location, normal scale, log-normal, gamma, logistic, Richards, binormal, and bilognormal of the Share Each Length’s Catch Total (SELECT) methodology. Bilognormal and normal scale models showed the best fit to the length frequency data of S. commerson and T. albacares respectively. The mean lengths of S. commerson were estimated to be 67.2 cm, 80.5 cm and 99.7 cm for hook #7, #6 and #5, respectively, while, the mean lengths of T. albacares were estimated to be 99.2 cm, 118.8 cm, and 147.2 cm for hook #7, #6 and #5, respectively. The results indicated that hooks #7 and #6 captured individuals lower than length at first maturity. Based on these findings, the study recommends the use of hook sizes that are above hook #6 for responsible exploitation of S. commerson and T. albacares in the GoM region. This strategy minimizes the capture of juvenile fish, promotes sustainable fishing practices, and supports marine conservation, while also contributing to species-specific fishery management in the GoM.

This study investigates the selectivity characteristics of monofilament trammel nets used by local fishers in the Gulf of Mannar (GoM) for two commercially important carnivorous fishes, Lethrinus lentjan (Lacepède, 1802) and Saurida tumbil (Bloch, 1795). The catch data were collected fortnightly from January 2024 to June 2024 with trammel net fishing operation from three different stretched inner panel mesh sizes (60 mm, 80 mm, and 100 mm). The number of fishes caught showed an inverse relationship with mesh size. As the mesh size decreased, the total catch increased for both L. lentjan and S. tumbil. The selectivity parameters were estimated using eight different models such as, normal location, normal scale, log normal, gamma, logistic, richards, binormal and bilognormal within Share Each Length’s catch Total (SELECT) method. Among these, the bilognormal model best described the selectivity pattern, exhibiting the lowest deviance values. The modal lengths of L. lentjan captured were 24.73 cm, 32.97 cm and 41.21 cm for the 60 mm, 80 mm, and 100 mm mesh sizes, respectively. Similarly, the modal lengths of S. tumbil were 23.87 cm, 31.83 cm and 39.79 cm. The smaller mesh sizes captured a higher proportion of juveniles, while larger mesh sizes selectively retained more mature fish. The Kolmogorov–Smirnov (KS) test confirmed significant differences in the length-frequency distributions across mesh sizes. The study recommends using trammel nets with an inner panel mesh size of 80 mm and above for capturing L. lentjan and S. tumbil, as this prevents the capture of juveniles and promotes sustainable exploitation, ensuring the conservation of these coral reef fish stocks in the GoM.

Mariappan, S.; Ravikumar, T.; Neethiselvan, N.; Dineshkumar, E.; Dhilipmaniraj, N.; Gomathy, V., and Manickavasagam, S., 2025. Economic and seasonal analysis on catch rate of fish traps operated along the coast of Thoothukudi, southeast coast of India. Journal of Coastal Research, 41(1), 49–56. Charlotte (North Carolina), ISSN 0749-0208. Fishermen along the Thoothukudi coast of India use arrowhead fish traps measuring 90 cm in length, 76 cm in breadth, and 40 cm in height. Direct observational surveys were conducted fortnightly from January 2022 to December 2022. Across 24 fishing trials, these traps yielded a catch of 2900 fishes, weighing 997.5 kg. Scarus ghobban exhibited a significantly higher mean catch per unit effort (CPUE) of 12.79 kg per trip than other species. The monthly mean CPUE for arrowhead fish traps was 41.6 kg per trip. Statistical analysis (analysis of variance) revealed that both species and season had significant effects on CPUE (p < 0.05), indicating notable variations in CPUE among species and across seasons. The pre-monsoon season exhibited the highest CPUE (51.8 kg per trip), followed by winter (51.1 kg per trip), monsoon (37.5 kilograms per trip), and postmonsoon (30.3 kg per trip) seasons, suggesting potential seasonal fluctuations in fishing activity or fish abundance, likely influenced by environmental factors such as weather and oceanographic conditions. The trap fishery at Therespuram fishing village showed promising economic benefits, with a benefit-cost ratio of 1.64. The study period revealed that traps operated at Therespuram fishing village were rigid, leading to limited traps being carried onboard fishing vessels. Consequently, the present study suggests that collapsible traps be employed to significantly reduce onboard space requirements. This adaptation would enable fishermen to carry more traps, potentially resulting in increased catches.

The study evaluated the length–weight relationship (LWR) and the relative condition factor (Kn) for 12 economically important pelagic reef fishes captured through experimental troll line fishing at the Kombuthurai fish landing center, situated along the Gulf of Mannar. From January to December 2024 a total of 3,096 specimens were collected. The experimental troll line gear was operated at depths ranging from 5 to 30 m, with fishing sessions lasting between 4 and 7 h. Logarithmic transformations of the data were applied to establish the LWR, and linear regression analysis was conducted to estimate the values of a and b for 12 fish species across six families under 11 genera. Notably, this study recorded new maximum lengths (Lmax) for a tuna species, Euthynnus affinis (106 cm). The estimated growth coefficient (b) values for 12 species displayed a significant variation (p < 0.005), ranging from 2.5892 (Epinephelus malabaricus) to 3.228 (Scomberomorus commerson) thus reflecting that fish species predominantly displayed allometric growth. In addition, almost all the fishes except Decapterus russelli (0.9544) exhibited a relative condition factor (Kn) of one or greater than one, thus implying that environmental parameters favor fish growth. These parameters offer valuable insights into ecological patterns, biology, fisheries, stock assessments, and species-level management.

The present study elucidates length–weight relationship (LWR) and relative condition factor (Kn) of 20 carangid fish species from two major fish landing centres along the coast of Gulf of Mannar, southeast coast of India. The sampling was carried out biweekly between June 2023 and May 2024 with commercial bottom trawl nets and bottom-set gill nets. Among the 20 species, LWR were established for 7 carangid species, (Alectis ciliaris, Atropus armatus, Caranx sexfasciatus, C. tille, Platycaranx talamparoides, Scyris indica and Turrum coeruleopinnatum) for the first time in Indian coast. Additionally, new maximum length (Lmax) were recorded for three species namely Atule mate, Caranx tille and Scomberoides commersonnianus along the Indian coast. The slope value ‘b’ ranged from 2.5632 (Ferdauia ferdau) to 3.2952 (Turrum coeruleopinnatum). Furthermore, all species, with the exception of Decapterus russellii (0.9488), exhibited Kn values of ‘1’ indicating that the environmental growth conditions were suitable for fish growth. These findings are crucial for assessing the relative condition of these fish stocks and developing conservation and management plans for their sustainable exploitation in the region.

This study aimed to evaluate the shelf life of a surimi gel-based fish bait (SGFB) made with lizard fish surimi gel and 5

Ravikumar, T.; Neethirajan, N.; Chandran, S.; Sangaralingam, M.; Natarajan, J.; Umamaheswar, T., and Padmavathy, P., 2024. Ichthyofaunal diversity from longline catches in the Gulf of Mannar (GoM), southeast coast of India. Journal of Coastal Research, 40(1), 115–128. Charlotte (North Carolina), ISSN 0749-0208. The present study aimed to document the spatial and temporal ichthyofaunal diversity of reef associated fishes caught with experimental longlines fitted with different "J" hook sizes (no. 12, no. 9, and no. 6) and shapes (Straight, Kirbed, and Reversed) from the Therespuram and Mundhal fish landing centres of Gulf of Mannar (GoM), Southeast Coast of India. Sampling was done at a fortnightly interval from February 2020 to January 2022. The total of 21,322 fish diversity includes 37 species of fish belonging to 15 genera, 10 families, and seven orders have been recorded during the study period. Order wise and species wise landing revealed the dominance of Perciformes with five families (Haemulidae, Lethrinidae, Lutjanidae, Nemipteridae, and Serranidae) and 28 species while in the case of order Centrarchiformes it represented with only one species. Fish diversity of GoM was assessed by calculating the various diversity indices such as Shannon–Weiner biodiversity index (H′) ranged from 2.31 to 3.29, Simpson's Dominance Index (1-λ′) ranged from 1.80 to 4.73, Pielou's Species Evenness index (J′) ranged from 0.90 to 0.99, and Margalef index (d) of species richness ranged from 2.03 to 4.73. The results of the present study revealed that the experimental longlines caught one endangered (3%), four vulnerable (11%), two not evaluated (5%), one data deficient (3%), and 29 species (78%) of least concern as per the International Union for Conservation of Nature status. The assessment is a prerequisite for understanding the biodiversity and to help fishery managers to evolve new strategies for the sustainable exploitation and conservation of coral reef associated fishes in this region.

The Length-weight relationships (LWRs) were estimated for 29 commercially important demersal reef fish species caught in the experimental longline fisheries from the Gulf of Mannar (GoM), India during December, 2019 to September, 2021. For this purpose, the experimental longline gear was operated between 20 and 50 m depths during from 3 to 5 hours. By using the logarithmic transformed data, linear regression analysis was performed to calculate a and b values for 29 fish species distributed under 5 families and 6 genera to establish LWRs. The estimated minimum and maximum allometric coefficient (b), coefficient of determination (r 2 ) and Fulton’ condition factor (K) were 2.6023 and 3.8743, 0.8493 and 0.9019, 1.3357 and 2.5846, respectively. This study reports a new maximum size for Lutjanus rivulatus (83 cm) for the whole world for the first time. In addition, the current study brings out information on LWR of fish species like Lethrinus ornatus , Lethrinus harak , Cephalopholis urodeta , Epinephelus polyphekadion and Epinephelus coeruleopunctatus for the first time in Indian waters in general and GoM in particular.

Manjunathan, M.; Ravikumar, T.; Chandran, S.; Neethiselvan, N.; Jawahar, P.; Arisekar, U., and Karthy, A., 2023. Catch efficiency and economic analysis for traditional fishing gear (troll lines) operated along the Coromandel and Gulf of Mannar coasts (southeast India). Journal of Coastal Research, 39(6), 1137–1145. Charlotte (North Carolina), ISSN 0749-0208. This study evaluated the effects of three different J hook types, single hook no. 6, double hook no. 6, and triple hook no. 8, on catch rate, catch composition, and economics of two traditional troll-line methods used along the southeast coast of India. Traditionally, the hand- and leg-held troll line has been used in the Gulf of Mannar (GoM), and the outrigger boom-held method has been used on the Coromandel (CoM) coast. The studies were conducted at fortnightly intervals between June 2020 and January 2021. The overall catch rate (no. h21) was found to be highest with the double hook (0.6 fish h21) and lowest with the triple hook (0.04 fish h21) on the CoM coast, while the single hook (0.34 fish h21) and triple hook (0.02 fish h21) showed the highest and lowest catch efficiency along the GoM coast, respectively. The catch composition was constituted by Scomberomorus commerson (36%), Auxis thazard (18%), Euthynnus affinis (16%), Caranx ignobilis (13%), Thunnus albacares (9%), Scomberomorus guttatus (7%), Coryphaena hippurus (0.8%), and Istiophorus platypterus (0.2%) in the GoM, while it was Thunnus albacares (45%), Euthynnus affinis (18%), Auxis thazard (14%), Istiophorus platypterus (7%), Coryphaena hippurus (6%), Acanthocybium solandri (5%), Scomberomorus commerson (3%), and Caranx ignobilis (2%) on the CoM coast. The chi-square test showed a significant correlation between hook type and fish composition (χ2 = 9650.6, df = 16, p < 0.05). The current study demonstrated a net profit improvement of 3313 rupees/trip at GoM and 2093 rupees/trip at CoM. The benefit-cost ratio (B:C) for GoM and CoM was calculated to be 1.84 and 1.76, respectively.

The study dealt with the development of biopolymer based hydrogel artificial fish bait with hydrolysates derived from fish processing wastes. Fish scale gelatin (FSG) was used for the development of a hydrogel to which bioattractants extracted from seafood processing wastes of fish, squid and shrimp were added to prepare composite gels such as FSG-FH, FSG-SH and FSG-SPH, respectively. To understand the homogenesity and cross linking complexation of composite gels, the study aimed at investigating physico-chemical, thermodynamic, molecular and structural properties were analysed. The gel strength, melting point and thermal stability of the composite hydrogels were found to decrease marginally compared to the control gel, FSG. It could be understood that the crystalline structure at 2 theta = 23 degrees of the FSG-SH, and FSG-FH were not much altered compared to FSG gel. However, alteration in the crystalline structure in FSG-SPH was evident at 2 theta = 27.3 degrees. The TGA and DSC analysis revealed the reduction in the thermal stability of FSG on the addition of protein hydrolysates in the process of coacervation to get hydrogel based fish bait. Further, FESEM and AFM analysis indicated FSG-SH as the composite hydrogel with most compact and smooth surface was evident by Ra and Rq values. Among the composite gels, FSG-SH was found to have higher hydrophobicity due to enhanced gel structure. FTIR spectra of FSG and composite gels exhibitted similarity corresponding to amide-A, B, I, II and III bands. However, NMR analysis revealed the existence of notable difference with respect to chemical shift in the range of 7.0-7.75 ppm expressing the presence of aromatic protons of the amino acid phe and N-H protons of amide in all the composite gels. Further, NMR analysis confirmed the role of imino acids (delta CH2 & beta CH2 protons) and hydrophobic amino acids (alpha-CH2 protons) in decrease the physical and thermal properties of the composite gels. The addition of protein hydrolysates with FSG was found to decrease the physical, thermal and structural properties, however improve the aromatic compounds of the composite gels.

The study dealt with evolving an artificial fish bait by incorporating bioattractant concentrates derived from seafood processing wastes by enzymatic hydrolysis namely fish waste concentrate (FWC), squid waste concentrate (SWC), and shrimp processing concentrate (SPWC). They were characterized based on amino acid content and presence of different functional groups using FTIR. Among them, SWC was found to have the highest amino acid content of 60.85mg/100 mg followed by FWC (42.21mg/100 mg) and SPWC (24.82mg/100 mg). The developed artificial fish baits were subjected to protein leaching, solubility in seawater besides testing for acceptability by the red snapper. The study revealed that the bait incorporated with SWC at 3% level was found be the most ideal, with the protein leaching rate of 24.82 mg/g/h, solubility rate of 36.6 mg/g/h and the attractability score of 29/30. The amino acid leaching rate was 3.11 mg/h/100 mg and it was found to contain five amino acids such as glycine, proline, glutamic acid, alanine and serine. The study revealed that the hydrolyzed squid waste concentrate can be incorporated at 3% (w/w) with fish gelatin based biomatrix during gelation to prepare artificial bait.

The length-weight relationships were estimated for three reef fish species caught in the Gulf of Mannar, India using experimental longlines. The longline fishing took place from December, 2019 to September, 2021 in fortnightly intervals, using longlines (2400 m, 2700 m and 3360 m each), equipped with each 600 various "J" type fishing hooks (straight, reversed, kirbed). The hook sizes used were standard size numbers 6, 9, and 12. The longlines fabricated with polyamide monofilament line were operated from 20 to 50 m depth for 3-5 hours each time. Overall, 81,000 hooks were deployed in 45 fishing trials. The total length and total weight of the combined sex group was recorded nearest to 0.1 cm and 0.01 g, respectively. By using the logarithmic transformed data, linear regression analysis was performed to calculate a and b values for three fish species to establish length-weight relationships. The parameters for the length-weight equations for three species are provided along with respective coefficient of correlation and the 95% confidence intervals. A new maximum total length was recorded for two grouper species, viz., Epinephelus faveatus (36.5 cm) and Cephalopholis urodeta (46.0 cm).

Extraction of gelatin from fish wastes and the development of artificial fish bait matrix using the extracted gelatin were attempted in the study. Biochemical composition of fish wastes (heads, skins, fins and scales) and the gelatin derived from the wastes of corresponding body parts and physicochemical properties of fish gelatin were analyzed. Considering high yield (19.8–22.4%), good gel strength (1.99–2.3 N), high melting point (27 °C) and simple extraction process, the scale gelatin was selected for the development of artificial fish bait matrix. To optimize the levels of gelling agent, cross linker and solvent for the preparation of bait matrix, RSM was adopted. Gel strength and insolubility ratio were analyzed to know the suitability of the bait. They were found to have the gel strength ranging from 1.3 N to 23.5 N, insolubility ratio from 55–83%, and melting point from 34.3 °C to 41.1 °C. The optimum levels of ingredients for the preparation of ideal bait matrix were standardized as: gelatin-25.5%, sucrose-22.5% and water-52%. The curing temperature and curing duration were optimized based on the optimum gel strength of 20.84 N and insolubility ratio of 74.5% was 5 °C and 25 h respectively. The study revealed that a developed fish bait matrix suitable for fishing can be made from gelatin derived from fish wastes.

Marine biology,marine ecology,Phytoplankton, marine algae, zooplankton, nekton, benthos, corals and coral reefs, ecology, zoogeography and systematics, primary production and experimental work on ecosystem including energy flow at different trophic levels, population dynamics and theoretical models, recycling of matter, influence of environmental factors on metabolic activity, marine microbiology, mariculture and experimental work on propagation of cultivable species, biology of fishes, marine reptiles, sea birds and mammals, physical, chemical, geological and meteorological features of the environments related to marine biology, marine environmental damage caused by pollution and engineering works, underwater observations, conservation of living resources, modifications in methodology and techniques and development of new apparatus related to marine sciences

Single-day trawling is commercially practiced along Thoothukudi coast, involving a total of 275 trawlers of varying length range operated from Thoothukudi fishing harbour (8°47’N, 78°9.5’E). The trawlers can be classified in three categories: vessels with overall length (OAL) of 40–50′ (Type 1), OAL 50–60′ (Type 2) and OAL above 60′ (Type 3). Trawlers with OAL of 45′, 55′ and 65′ were selected for the study. Irrespective of the type of vessel, the power required for towing the net was found to be unnecessarily high. The excess power wasted due to faulty trawl designs in Type-1, Type-2 and Type-2 vessels was 55, 87 and 133 hp, respectively. While trawling with optimal trawl design would contribute only 28.67% of the brake horse power (BHP) of the Type 3 vessels, the existing design of trawl used in this type of vessels contributed as much as 50.83% of the BHP. The Type-1, Type-2 and Type-3 trawlers were found to operate with excess fuel consumption at the rate of 103, 212 and 418 L of diesel per cruise, respectively. Based on the annual fuel consumption, true total annual CO2 emission was estimated as 458 tons. The study revealed that the total fuel consumption can be reduced by 40% by optimizing the trawl design and reducing the free-running speed, free-running duration and trawling speed. Further, vessels with an OAL of 60′ and above may be permitted for multi-day fishing in distant waters after suitably limiting the number of fishing trips/month in order to minimize the fuel loss through free running.