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Vasanth, K.; Muthupandi, K.; Naganandhini, V.; Radhakrishnan, K., and Narayanan, M., 2025. Length-weight relationships of eight pelagic fish species caught by drift longlines in the Gulf of Mannar, India. Journal of Coastal Research, 41(3), 510–515. Charlotte (North Carolina), ISSN 0749-0208. The length-weight relationships were estimated for eight pelagic species caught in the Gulf of Mannar, India, using experimental longlines. The experimental study was conducted from January to October 2022 in fortnightly intervals using longlines (3000 m for needlefish and 11,250 m for carangids), each equipped with 600 “J”-type fishing hooks of various types (straight, reversed, kirbed). The hook numbers used were standard sizes that ranged from 8 to 11 for both groups (needlefish and carangids). The longlines were fabricated with polyamide monofilament and operated from 1 to 2 m depth for needlefish and 20 to 25 m depth for carangids for 3 to 5 hours for both longline units. Overall, 21,150 hooks were deployed in 24 fishing trials for each experimental longline. A maximum total length was recorded for four needlefish species, Strongylura strongylura (80), Tylosurus choram (91), Tylosurus crocodilus (97), and Ablennes hians (96), and four carangids species, Caranx bajad (60.5), Alectis indicus (62), Caranx ignoblis (69), and Scomberomorus commerson (74). In terms of growth, the length-weight relationships revealed positive allometric growth (b >3) for three species of carangids, C. bajad, S. commerson, and A. indicus (p < 0.05) and negative allometric growth (b <3) for four species of needlefishes, T. choram, S. strongylura, T. crocodilus, and A. hians, and one species of carangid, C. ignoblis.

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 (L max ) 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.

Competition, predation and facilitation shape community structure. Yet facilitative behaviour is poorly studied, especially in marine ecosystems. We investigated the diet and foraging behaviour of 5 Afro-Palaearctic migratory seabirds during their non-breeding period in West Africa, focussing on their facilitative associations with predatory fishes. We used next-generation sequencing to describe the diet of 5 tern species, employing DNA metabarcoding for the identification of prey from droppings. This is the first time this method has been used for studying the diet of non-breeding migratory seabirds. Our results showed a high diet overlap among all seabirds, mostly due to the dominance of a single prey species, Sardinella maderensis (with a mean frequency of occurrence of 90% in tern diets). The subsurface marine predators identified in association with terns were crevalle jack Caranx hippos and West African Spanish mackerel Scomberomorus tritor, 2 predatory fishes which also rely on Sardinella maderensis as their most frequent prey in the study area, the Bijagós Archipelago. There were marked inter-specific differences in the reliance of terns on subsurface marine predators as facilitators, ranging from completely independent (little tern Sternula albifrons) to near-obligatory (black tern Chlidonias niger). The varied feeding strategies and small-scale spatial segregation may explain the co-existence of the 5 tern species during the non-breeding period, preying mostly on the same clupeids. Declines both in predatory fishes and in Sardinella maderensis and other clupeids are likely to impact the long-distance migrant seabirds studied here, calling for integrated management of fisheries in these coastal ecosystems.

Petroleum platforms in the U.S. Gulf of Mexico (GOM) are important habitats for fishes and support regional fisheries. However, drivers of the horizontal (i.e., latitudinal and longitudinal) and vertical (i.e., position in the water column) distribution patterns of fishes associated with these artificial habitats are not fully understood on a GOM‐wide scale. To build upon previous studies on a large spatial scale and focus on species‐specific drivers, we conducted 114 submersible rotating drop‐camera and water quality sonde surveys at 54 platforms throughout the GOM. We then fitted two sets of binomial generalized additive mixed models integrating environmental and structural (i.e., characteristics of platforms) predictors to encounter/nonencounter data for 17 fish species so as to understand their horizontal and vertical distribution patterns throughout the GOM in platform habitat. Significant predictors for horizontal distribution included distance from shore (for Bermuda Chub Kyphosus saltatrix, Greater Amberjack Seriola dumerili, Vermilion Snapper Rhomboplites aurorubens), salinity (Bermuda Chub, Red Snapper Lutjanus campechanus), the number of platforms within 5 km (Blue Runner Caranx crysos, Crevalle Jack Caranx hippos), and dissolved oxygen concentration (Red Snapper). Significant predictors for vertical distribution included temperature (for Atlantic Spadefish Chaetodipterus faber, Bermuda Chub, Blue Runner, Greater Amberjack, Red Snapper), salinity (Greater Amberjack, Red Snapper), dissolved oxygen concentration (Red Snapper), and seafloor depth (Red Snapper). However, the majority of the study species were not influenced by the predictors included in the horizontal (11 of 17 species) and vertical distribution (12 of 17 species) generalized additive mixed models. Thus, many GOM fishes were found to associate with platforms over a relatively wide range of environmental conditions and platform characteristics. This suggests specific environmental conditions and distinct platform characteristics may not be as important as the simple number of available platforms for determining the distributions of many platform‐associated fishes in the GOM.

Although myoglobin (Mb) has been considered to be one of the well-characterized proteins, screening of post-genomic era databases revealed the lack of adequate information on teleost Mbs. The present study was aimed to investigate stability and functional features of Mbs from three teleosts of the same family. To unfold how primary structure influences the stability and function of proteins, Mbs were purified from the dark muscles of three carangids, namely, yellowtail, greater amberjack, and silver trevally. Thermostabilities measured by circular dichroism (CD) spectrometry revealed species-specific thermal denaturation pattern, i.e., silver trevally > yellowtail > greater amberjack Mbs. On the other hand, autoxidation rate constants of the ferrous forms of those three carangid Mbs showed positive correlation between the ferrous state of the heme iron and rising temperature. The order of autoxidation rate was in the order of greater amberjack > yellowtail > silver trevally Mbs. The finding of the present study denotes that the thermal stability is not necessarily correlated with the functional stability of carangid Mbs even though their primary structures shared high homology (84–94%).

Studies on cymothoid isopods as parasites affecting the marine fisheries and aquaculture industries are relatively scarce in the Philippines despite having detrimental impacts on their fish hosts. Parasitological examination on the bigeye scad, Selar crumenophthalmus (Bloch, 1793), a potential aquaculture species, in the waters of the Sibuyan Sea, Philippines was done on fish specimens collected on 21 April 2021. Out of the 88 specimens, a total of 13 big eye scads were infected with cymothoid isopod Norileca indica (Milne Edwards, 1840), found in the branchial cavities of the fish, resulting in a prevalence of 14.77%. A total of 20 individual isopods (13 females and seven males) were recovered, with a mean intensity of 1.53. Based on the morphological characteristics and as confirmed by the cytochrome oxidase subunit 1 ( CO1 ) sequence, one host fish was also infected with Ceratothoa carinata (Bianconi, 1869). This appears to be the first record of C. carinata from the Philippines. To fully understand the implications of cymothoid parasites on the bigeye scad, further studies are recommended to account for the impacts of seasonality, reproductive stages of the host fish, and effects of abiotic factors such as water movement and depth.

Background. Atlantic horse mackerel, Trachurus trachurus (Linnaeus, 1758), is among bento-pelagic species subject to discard within deep-water rose shrimp fisheries, and how such species would react to light wavelength is therefore important, to be consistent with the Common Fishery Policy (CFP). Despite the existing literature currently available, there is still paucity of relevant information about how artificial light wavelengths affects the behaviour of T trachurus juveniles. In this context, the effects of different artificial light wavelengths on some behavioural features of juvenile T. trachurus were investigated. Materials and methods. Maintained in a fish tank, the juveniles of Atlantic horse mackerel, after acclimatization, were subject to six different light wavelengths, representing the following colours: white, violet, blue, green, yellow, and red. Subsequently, behavioural features, specifically phototaxis (degree of attraction or repulsion toward the light source) were tested. Results. By phototaxis per light wavelength, the studied juvenile individuals produced statistical differences in the presence frequency (P< 0.05) revealed by blue that noticeably attracted some, relative to the white light that repulsed others. Yet, violet and red lights produced much less but no significant attraction of these juveniles (P > 0.05). Conclusion. The presently reported study has provided additional information about ecological knowledge and understanding specific to juvenile T trachurus individuals, which can further the development of (selective) light fishing techniques, aimed at reducing unwanted catches of commercial pelagic fisheries.

This contribution presents stock assessments for ten fish and two squid populations exploited by Chinese, South Korean and Japanese fishing fleets in the Tsushima Warm Current region, i.e., West of Japan and East of China. The methods used are a Monte Carlo method (CMSY) and a Bayesian state-space implementation of the Schaefer model (BSM), based on published time series of catch and abundance data (SSB and CPUE). Results show that two fish stocks, Japanese jack mackerel (Trachurus japonicus) and yellowback sea-bream (Dentex hypselosomus) are in a healthy status, while daggertooth pike conger (Muraenesox cinereus) appears to have collapsed. The other nine stocks show varying degrees of overfishing. The cooperation of several countries will be required to recovery the fishery resources in the Tsushima Warm Current region.

To study the diet of the swordfish (Xiphias gladius) in the Strait of Gibraltar, a total of 176 stomachs were examined from the Moroccan artisanal fishery targeting this species, from April to September 2015. The frequency of occurrence (FO), percentage in number and in weight of prey as well as the per cent index of relative importance of prey (%IRI) were calculated to assess the diet preferences of swordfish in relation to its body size, sex and month. Our findings confirm the opportunistic feeding behaviour of swordfish. The prey items consist primarily of fish (54.6% in number and 82.7% in weight), followed by cephalopod (43.36% in number and 17.25% in weight). The Atlantic horse mackerel (Trachurus trachurus) and the southern shortfin squid (Illex coindetii) are the most important prey, with a % IRI of 47.54 and 35.04%, respectively. The results revealed that there are no significant differences in the diet preferences among sexes and size classes. However, diet composition varied significantly among months. A significant correlation was found between the body length of predator and prey size. The remarkable decrease in the fullness index (fi) from June to August suggests that swordfish were in a spawning condition, with reduced feeding.