Abdul Wahab Khan
Panaji
A study has found the Indian oil sardine — Sardinella longiceps — constitutes a single morphological stock along the entire west coast of the country, providing a new clarity on the complex stock structure of the fish variety, a staple of the Goan plate.
The research, published in the peer-reviewed journal Thalassas: An International Journal of Marine Sciences in April 2025, deployed an intricate geometric technique known as truss morphometry to settle a decades-old scientific dispute.
The study was led by HG Shetye of the College of Fisheries, Shirgaon, Ratnagiri, in collaboration with SS Gangan, BM Yadav, and PH Sapkale of the Taraporewala Marine Biological Research Station, Mumbai, along with VH Nirmale and SY Metar of the College of Fisheries, Ratnagiri.
Together, they examined 326 specimens collected from four landing centres — Ratnagiri, Panaji, Mangaluru, and Kochi — between September 2023 and January 2024.
The impetus for the study was the persistent uncertainty surrounding the species’ population structure. Landings of the fish along India’s west coast have fluctuated dramatically — from 2.07 lakh tonnes in 2017 to a worrying low of 0.28 lakh tonnes in 2020, recovering to 2.13 lakh tonnes by 2022.
Climate drivers such as sea surface temperature, the El Niño-Southern Oscillation, and the Pacific Decadal Oscillation have been cited as contributing factors. Yet without clarity on stock identity, effective fisheries policy has remained elusive.
Using network of ten anatomical landmarks across each fish’s body — from the tip of the snout to the base of the caudal fin — the team calculated 21 truss distances to build a detailed morphological profile of each specimen. Statistical tools including MANOVA, Principal Component Analysis (PCA), and Discriminant Function Analysis (DFA) were then applied. The PCA extracted six principal components accounting for 79.4 per cent of total morphological variance, with the most significant variations concentrated in the head region, body depth, and caudal fin area.
Findings regarding Goa have offered a glimpse into the migratory nature of the species.
Interestingly, the sardines from Panaji and Mangaluru showed the lowest classification accuracies—51.9 per cent and 63.0 per cent respectively—indicating a high degree of similarity.
The report has said that this is likely due to their “geographical proximity”, which results in “similar environmental influences and a higher degree of gene flow”. In contrast, the most significant divergence was found between the geographically distant populations of Maharashtra and Kerala.
The detailed results revealed that while 19 out of 21 morphometric characters showed significant differences across locations, there was “considerable intermingling of stocks”.
The researchers have observed that “the significant overlap among stocks suggests that these populations are not entirely distinct”. This intermixing is attributed to the sardine’s status as a highly migratory species, which “reduces the chances of reproductive isolation or distinct spawning grounds”.
The team has explained that variations in head structure or body depth often relate to local habitat factors like water turbidity, oxygen levels, or food availability.
However, the study ultimately concludes that “S. longiceps can likely be managed as a single stock along the west coast of India”. This alignment with previous genetic studies supports a unified management approach rather than fragmented regional policies, ensuring the long-term sustainability of this vital marine resource.
