Search

This is CMLRE contribution no. 158.-- 14 pages, 7 figures 5 tables.-- Data availability statement: Data will be available on personal request to the corresponding author, Morphology of the fish and otoliths are popularly used in the discrimination of species/stocks/populations and also to gather meaningful conclusions about their ecology. This approach is useful to enhance our understanding of the relationship between form and function in fishes when a direct assessment is impossible. Inter-species variation was analysed using geometric morphometric analysis for fish body shape, while morphometry and wavelet functions for sagittae morphology. A clear ecomorphological pattern in the body, as well as otolith shape, is evident among species as deeper inhabiting species possess a deeper body with oblong otoliths compared with shallower species that possess a more streamlined body with fusiform otoliths. We also observed that deeper species (P. obscura) possess bigger eyes for the optimum use of available light and bigger otoliths with higher otolith sensory area and otolith area ratio (S:O) for better sound reception capacities. Our hypothesis supports that the differences in fish morphological as well as sensorial traits (otoliths), which are closely related to their locomotion, foraging pattern and depth of habitation, lead to trophic segregation which in turn encourages their coexistence. This is the first work that discusses the relationship between body shape, otolith morphometry and morphology in deep-sea fishes and their ecomorphological interpretations, The financial, technical and logistical support from CMLRE is thankfully acknowledged, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

The present study reports observations of 13 giant freshwater whipray (Urogymnus polylepis) from commercial fish landings along the north-east coast of India and updates existing records based on field observations and local social media reports. The disc width of the landed specimens ranged from 120 to 223 cm and they weighed 95-300 kg. All 13 specimens observed were mature (nine females and four males) and three females were pregnant, with embryo numbers ranging between 4 and 15. Globally, U. polylepis is listed as 'Endangered', and greater protection measures are needed in India to assist in reversing current population declines.

Investigations were carried out to determine the nutritional profile of Indian Ocean swimming crab Charybdis smithii, which is emerging as an unconventional resource in trawl discards of India. The average protein content was 9.38 g/100 g, fat 0.86 g/100 g, ash 0.34 g/100 g, fiber 0.13 g/100 g, and carbohydrate 1.8 g/100 g. One-way analysis of variance showed no significant variations of constituents except in dry matter and carbohydrate between sexes. Macronutrients, Na (317.1, 327.6/100 g), K (148, 177.40 mg/100 g), Ca (187.90, 285.80 mg/100 g), and Mg (34.31, 41.49 mg/100 g), showed significant variation between sexes. The composition of micronutrients in male and female were Cu (0.28, 0.15 mg/100 g), Fe (0.57, 0.71 mg/100 g), and Zn (1.71, 2.75 mg/100 g). Mineral content showed significant difference between sexes. Amino acid analysis showed that 12.04 and 11.47 g/100 g essential amino acid glycine was present in male and female, respectively, and lysine concentration was 13.96 and 12.65 g/100 g, respectively. The nutritional profile of the species was determined the first time and shows that it is comparable with any other edible crabs and could be exploited as a commercial resource to supplement nutritional demand.

Length-weight relationship (LWR), condition factor, sex ratio, gonadosomatic index (GSI) hepatosomatic index (HSI) of the smooth blaasop puffer fish Lagocephalus inermis (Temminck and Schlegel, 1850), an emerging fishery resource along south-eastern Arabian Sea were studied from 1,722 samples collected during August 2017-May 2019 from Mangalore Fishing Harbour, Karnataka, India. LWR indicated negative allometric growth [W = 0.034805L2.76 (males); W = 0.033574L2.78 (females), W = 0.033979L2.77 (pooled)] and significant difference was observed in the b value of the fishes. Sex ratio was 1:1.08. The ratio was unusually high during post-monsoon and Chi-square test revealed that the monthly sex ratio did not vary significantly throughout the year except for December and January (p

Red sea bream iridovirus (RSIV) is an emerging viral pathogen having significant socio-economic and environmental impacts on marine and brackish aquaculture systems. The study documents certain interesting findings of an RSIV disease outbreak that caused 50% cumulative mortality among cage farmed Asian sea bass in India. The confirmatory diagnosis was made based on internationally approved protocols. The affected fish showed splenomegaly, anaemia, and abnormally enlarged cells within the spleen, liver, kidney, and brain. The consistent presence of two fish pathogens, viz., Vibrio alginolyticus and Vibrio fluvialis, in the liver, along with characteristic vibrio-induced pathologies were noted, indicating the possible role of these bacterial pathogens in RSIV pathogenesis during the outbreak. More strikingly, the surviving fish were found to carry the virus even after two months post-outbreak, warranting future investigations on the carrier status of RSIV survivors. Transmission electron microscopy in the survivors demonstrated atypical virus particles within the degenerated cells of the vital organs, suggesting the role of host immune response in preventing the maturation of RSIV particles in the survivors. Phylogram based on MCP and ATPase genes demonstrated the spread of the same RSIV clone across different countries, regardless of the fish species. Results also revealed the presence of two RSIV subtypes. Both subtypes were mainly distributed in marine demersal fishes of Asian countries. Presently, subtype 2 is the most frequently reported one. Subtype 1 revealed higher genetic diversity with a wider geographical spread and host range. Molecular analyses revealed that MCP and ATPase genes could be targeted in RSIV subtyping, with MCP as a better candidate. A purifying selection was observed on the MCP gene that can be applied for diagnostic protocols. In short, the study generates certain thought-provoking insights on RSIV through the analyses of a recent outbreak along with the genetic and epizootiological data of global strains. Further, the paper also forms the first report on the presence of RSIV in surviving fish post-disease outbreak in the absence of clinical signs. Altogether, the results highlight the necessity of strengthening quarantine and RSIV diagnostic measures to have sustainable aquaculture practices.

The effectiveness of GIS-based resource mapping to strengthen the database for Ecosystem-Based Fisheries Management (EBFM), was tested in an attempt at resolving the existing gap in the data on non-commercial resources. In this paper we describe the result of that try by giving an example of one of the most important influential species in the benthic ecosystem of the Southeast Arabian Sea (SEAS). An estimated 2803 t of Charybdis hoplites, a relatively little known species from the coast, are yearly caught and discarded by trawlers operating from the Mangalore fisheries harbour. A GIS-aided study on distribution and abundance estimated, that the average biomass of the species is 322.7 t, at any time in the area covered. This study brings out the fact that a number of non-commercial biota are serving as non-detectable factors in sustaining productivity. The identification of their role and the quantification of their biomass thus constitute important data for an effective implementation of EBFM.

The relative abundance and biological characteristics of the spadenose shark Scoliodon laticaudus, from the south eastern Arabian Sea along Karnataka, India was studied. The average annual catch of the species during the period 2012–2017 was estimated at 112 t which formed about 13% of the total shark landing in the region. The species is landed mostly by trawl nets. Monthly abundance estimates showed that highest landing of the spadenose shark was observed in January. A total of 852 specimens were studied for biological characteristics. The length range of 19–63 cm was observed and length group of 45–55 cm formed the mainstay of the fishery. The length weight relationship for male and female and sexes pooled were 0.06588 L2.2386; 0.01118 L2.7497 and 0.01396 L2.6840 respectively. Analysis of covariance showed significant differences between the male and female ( p 0 . 05 ). In the present analysis, the regression co-efficient ( b value) for the species differs significantly from the value 3 indicating allometric growth. Lm50 for female and male were estimated as 32 and 33 cm. Chi-square-test on monthly sex ratio for the period showed that there was significant difference in sex ratio only in the months of January, October and November. S. laticaudus was found to be predominantly piscivorous in diet. The fishery is declining and efforts have to be taken for sustainable exploitation of resources.

The present study aimed to elucidate the length-weight relationship and growth parameters of the moonfish Mene maculata (Bloch and Schneider, 1801) along the Karnataka Coast. The species showed positive allometric growth with pooled ‘b’ value of 3.390 which is significantly greater than 3 (p

Scomberomorus commerson were collected on weekly basis during January 2012 to December 2014 at Mangalore Fishing Harbour. Stomach of 214 narrow barred Spanish mackerel measuring from 48 to 105 cm fork length (FL) for males and 45.5 to 115 cm FL for females were analysed to study their feeding habits. Fish with empty stomach were prevalent in almost all the months. Prey mainly comprised of fishes and crustaceans, with the fish component forming 99.9%. The index of relative importance (IRI) showed that the dominant prey were semi-digested fish remains (44.6%) of Sardinella longiceps (30.1%), Decapterus sp. (18.7%), whitebaits (2.5%), Rastrelliger kanagurta (1.5%) and Epinephelus spp. (1.1%), while Saurida sp. (0.7%), Megalaspis cordyla (0.5%), Scombroides sp. (0.2%) and shrimps (0.1%) were found occasionally in the gut. Index of stomach fullness (SFI) was 0.11 in August and 0.65 in January. Generally, SFI was higher during September to January and lower during February to August. The empty stomach ratio (ESR) ranged from 33.3% (August) to 92.3% (April).

Environmental parameters influence the productivity and abundance of fish in marine ecosystems. In this study, we attempted to analyse the relationship between environmental parameters and abundance of fish in trawling grounds in south-eastern Arabian Sea along the coast of Karnataka. Among the 85 species of finfishes and shellfishes caught in the trawling grounds, 41 finfish species, 24 crustaceans, 18 molluscs and two echinoderms were recorded. Seasonal differences were seen in biomass with the highest biomass during the post-monsoon period (October-January). Water temperature and nutrients were the key contributing factors of seasonal differences in the biotic communities studied. Season specific diagnostic species were identified using SIMPER analysis. Squilla which formed the major prey item of most of the demersal fishes dominated (>40%) coastal grounds throughout all seasons. This could be considered as a fishery indicator of the region. The dominance and abundance of copepods was found to be influenced by sea surface temperature (SST) and nutrients. The results of the study have implications on the fishery, knowledge on environmental factors influencing the abundance and importance of non-commercial species in sustaining the fishery in the region.

The feeding regime of organisms depend on the plankton community structure which is being studied worldwide to assess the changes in marine ecosystem structure due to climate change or anthropogenic activities. An attempt is made here to study the seasonal and long term variation in feed composition of Indian mackerel over a period of 40 years and its relationship with sea surface temperature to elucidate structural changes in food composition if any over period of time and its relationship to the primary and secondary productivity in eastern Arabian Sea marine ecosystem. The diet study during 2011-2014 reported the domination of phytoplankton consisting of Coscinodiscus sp. consistently and the presence of macroplankton and fish larvae whereas the diet during 1960-1961 showed the dominance of zooplankton and copepods. It could be assumed that increase in sea surface temperature which resulted in dominance of phytoplankton community as reported elsewhere in the world is also observed in eastern Arabian Sea which is reflected in the diet regime of Indian mackerel. The results also indicate its facultative feeding behaviour by compensating the low value phytoplankton with high value macroplankton and hence can be considered as a resilient species with regard to climate change.

Growth response of Crassostrea madrasensis to varying environmental factors in the Mulki estuary of Karnataka was investigated from April 2004 to March 2005. Temperature, salinity, pH, particulate organic matter (POM), particulate inorganic matter (PIM), total particulate matter (TPM) and chlorophyll a (Chl a) levels were correlated with growth in shell length. Marked seasonal patterns in growth rate were observed in relation to changes in environmental factors. Growth curve indicated a rapid phase (16.21±1.2 mm month-1) initially (May-June) followed by a slow phase (0.8±0.52 mm month-1) coinciding with the drop in salinity (August-September). Considering the temporal variations of environmental factors, their influence on growth rate was analysed seasonally. The growth rate was significantly correlated with Chl a concentrations in all the seasons. A pronounced seasonal cycle was noticed in Chl a levels resulting from blooms in pre-monsoon (April-May) and post-monsoon (October) seasons