Northwest Coast Of India Research Articles

Carbon isotopic and biochemical fingerprints of sedimentary organic matter in lower Narmada and Tapi rivers, north-west coast of India

ABSTRACTSources of organic matter (OM) in lower Narmada and Tapi river-estuaries were examined using organic carbon to nitrogen ratio (Corg/N), stable carbon isotope ratio (δ13Corg) and lignin phenol biomarkers. The signature of lower Corg (av. 0.50%) and higher δ13Corg (av. –20.3‰) in Narmada and, higher Corg (av. 0.85%) and lower δ13Corg (av. –22.8‰) in Tapi highlight the difference in OM characteristics of both systems, nevertheless they flow adjacent to each other. The OM in Tapi was predominated by fresh plant tissues, as indicated by higher Λ8 = 1.2–3.2 mg/100 mg Corg, lower Ad/Alv = 0.22–0.46 and lower LPVI = 17–23. The plant OM present in the sediments of Narmada was previously degraded and mixed with soil. The OM contribution from algae was restricted to estuarine stations in both the rivers, which was ∼50% in Narmada and ∼35% in Tapi. The contribution of OM from fresh vascular plant was higher (20% to 63%) in Tapi than Narmada (2% to 35%). This study illustrated the benefits of using lignin phenols along with Corg/N and δ13Corg to identify the potential OM sources in two large river–estuary systems of India, which highlighted the complex interaction of natural and anthropogenic processes acted on the terrestrial OM compositions.

First Record of Longspine Grouper, Epinephelus longispinis (Kner, 1864) from Gujarat, North-West Coast of India

A single specimen of longspine grouper was collected at a depth of 30–40 m by a single day trawler from the waters of Gujarat. The species is considered as ‘least concern’ by IUCN. The fish was examined for key morphometric and meristic characters such as body length and depth, head length, fin lengths, spine and rays counts, lateral line scale count, gill rakers count, shape and distribution pattern of spots on the body. The present study reports the first record of the species from north-west coast of India describing its extension of geographical distribution and addition of one more species to the biodiversity of Gujarat.

A case study on dol net fishing operation and its economic analysis off Gujarat, north-west coast of India

Dol net is traditionally used for fishing along the north-west coast of India. In this study, the operational as well as economic aspects of dol net operation off Navabandar, Gujarat was studied. Dol nets operations from mechanised boats locally called as Van along Navabandar coast were considered for the present study. The overall length (OAL) of the mechanised vessels were in the range, 10-12.8 m with 2.4-3.6 m breadth and 1-1.8 m height. The total capacity of vessels was in the range 15-20 t and average fish holding capacity was 2.5 t. The fishing vessels had six cylinder engines of 87 to 105 hp. Fishermen themselves fabricated the nets for the dol net, which had seven different parts with various lengths. Kaba-sus system using steel pipes was the method of dol net fishing off Navabandar. They were locally known as Bochi, Patiya, Aor, Trijo, Bangu, Chothi and Jalo. The study indicated that the profit of a dolnetter at Navabandar in a year was `2,88,122.

Longtail tuna fisheries in the northern Arabian Sea off the north-west coast of India: Moving towards developing spatially explicit fisheries management strategy

Longtail tuna (Thunnus tonggol, Bleeker, 1851), the largest growing species among neritic tunas have a unique distribution pattern globally. Northern Arabian Sea together with the Oman Sea and Persian Gulf in the north-western Indian Ocean is considered to be the major area where the species is abundant and form sizeable fisheries globally. India has an artisanal tuna fishery and contributes nearly 10% of the longtail tuna landing in the region, with Gujarat alone contributing nearly 80%. The paper updates on the longtail tuna fisheries in the region with focus on the north-west coast of India together with its spatial characteristics. Clues on the areas of abundance of the species along Gujarat coast over the seasons and temporal movements of different ontogenetic stages in the shelf areas are revealed. The study sets prelude to a cost effective and participatory collection of spatially referred data on the artisanal and small scale fisheries in the region.

Reproductive biology, diet and feeding pattern of longtail tuna Thunnus tonggol (Bleeker, 1851) in the north-eastern Arabian Sea off Gujarat, India

Longtail tuna <em>Thunnus tonggol</em> (Bleeker, 1851) is the major tuna resource in the neritic realms of the northern Arabian Sea and forms considerable fishery in the coastal nations in the region. Gujarat, on the north-west coast is the major province landing longtail tuna in India. The paper attempts to add to the hitherto sparse knowledge base on biology of the longtail tuna fished along the north-west coast of India, through a study spanning from 2011 to 2015. Reproductive biology, spawning, food and feeding dynamisms of the species were investigated. Sex ratio of the species was estimated as 1:2.1 and depicted an increase in male preponderance as the size increased. The fish attains maturity at 607 mm and it spawns during summer months starting from May. The fish is typically a non-selective feeder and over 22 taxa comprising of fishes, cephalopods and crustaceans formed the diet at varying rates over the year. Variation in feeding intensity at different reproductive stages is discussed besides the constraint posed by the large presence of unidentifiable, partially digested gut content.

Non-target species interactions in tuna fisheries and its implications in fisheries management: Case of large-mesh gillnet fisheries along the north-west coast of India

Non-target species interactions in tuna fisheries and its implications in fisheries management: Case of large-mesh gillnet fisheries along the north-west coast of India

Studies on Population Characteristics of Frigate tuna, Auxis thazard (Lacepede,1800) Occurring in the North West Coast of India

Studies on Population Characteristics of Frigate tuna, Auxis thazard (Lacepede,1800) Occurring in the North West Coast of India

Investigations on the age, growth and mortality parameters of Kawakawa, Euthynnus affinis (Cantor, 1849) from the North west coast of India

Kawakawa, Euthynnus affinis contributes to the tune of 35,466 tonnes forming 1% to the total marine fish landings of India. Investigations on growth and mortality were of this species carried out based on the length frequency data during 2008-2012. The length-weight relationship for the pooled samples were derived for intercept a=0.0286, slope b=2.857 and coefficient of determination r 2 =0.917. The values obtained for growth parameters of L∞ was 67.86 cm, for growth coefficient (K) 0.70 and for t o -0.26y -1 . The natural, total and fishing mortalities recorded as 0.86, 1.48 and 0.62 y -1 ,respectively. The exploitation ratio (F/Z) was observed as 0.42. The M/K ratio was estimated at 1.23. The average fork length of 46 cm and weight of 2024 g were estimated in the samples collected. The length at the end of 1 st year to 5 th year was observed to be 33, 52, 64, 70 and 75 cm, respectively. The fishing mortality derived in this study is more than the optimum and limit value indicated the sign of overexploitation.

Genetic variations among white spot syndrome virus (WSSV) isolates from shrimp farms in Gujarat, north-west coast of India

The present paper documents the molecular diagnosis and genotyping of white spot syndrome virus (WSSV) isolates collected from different shrimp farms of Gujarat, north-west coast of India. Preliminary diagnosis was done using singletube PCR and genotyping of isolates by analysis of variable number tandem repeat sequence (VNTRS) in minisatellites viz., ORF 94, ORF 125, ORF 75 and ORF 75 flank. Out of the 79 samples analysed, 32 (33.80%) were positive with low (54.17%), medium (8.33%) and high (37.50%) severity of infection. Genotyping, using ORF 94 revealed that repeat units (RUs) 4 and 11 were the most frequent ones (32%) while ORF 125 showed 5 different repeat types of which RU 5 was the most common (45.83%). Two genotypes were observed for ORF 75, one showed multiple repeats of two 45 bp, followed by a 57 bp, whereas the other showed two repeats that included 5 and 4 repeats of 45 bp. Sequence analysis of the 54 bp variable sequence of ORF 94 RU type 4 revealed single-nucleotide polymorphism (SNP) at 47th base. Based on the results from ORF94, dominance of RU types 11or 4 were recorded for the first time in India and one sample showed 2 bands of different sizes indicating the prevalence of two different genotypes infecting the same pond at a given time. Further, no correlation could be observed between the virus genotype and the severity of the mortality in the outbreaks. The results suggest the widespread occurrence of WSSV in the region and circulation of distinct virus genotypes.

Reproductive biology and diet of the grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhinidae) from the north-eastern Arabian Sea

Information on reproductive biology is presented for the grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhiniformes), collected off the north-west coast of India in the Arabian Sea. A total of 711 individuals, of 27.0 to 93.0 cm total length (TL), 180 to 2600 g total weight (TW) were used for the study. The lengthweight relationships were significantly different between the sexes. The size-at maturity (Lm50) for females and males was estimated to be 62.3 and 59.5 cm TL respectively. Number of embryos ranged from 1 to 7 and the size at birth was estimated between 25 to 30 cm TL. Overall sex ratio favoured the females slightly at the rate of 1.27:1. There was significant positive correlation between maternal TL and number of embryos (p<0.001). Dietary analysis of stomach contents (%IRI) revealed that R. oligolinx feeds primarily on teleosts (95.5%), cephalopods (3.2%) and crustaceans (1.2%). This study presents the first detailed biological observation on size, sex composition, size-at-maturity (Lm50) and length-weight relationship of R. oligolinx from the northern Arabian Sea.

Population dynamics and stock assessment of grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhinidae) from the north-west coast of India

The life history and exploitation parameters of Rhizoprionodon oligolinx Springer, 1964 were assessed using commercial landing data of 2012-2015 from Mumbai waters of India to understand the population dynamics and stock status of the species. The average annual landing of the species was estimated to be 383 t, which formed about 9.1% of the total shark landings of Maharashtra. L∞, K and t0 estimated were 97.1 cm, 0.47 yr-1 and -0.79 yr respectively. Total mortality (Z), fishing mortality (F) and natural mortality (M) rates were estimated as 2.16 yr-1, 1.48 yr-1 and 0.69 yr-1 respectively. The length at capture (L50), length at female maturity (Lm50) and male maturity (Lm50) were estimated as 49.7, 62.3 and 59.5 cm respectively, which indicated that most of the sharks entered peak phase of exploitation before attaining sexual maturity. Length-weight relationship indicated allometric growth (b>3) for the species. The species was found to be a continuous breeder and showed peak recruitment during April. The current exploitation rate (Ecur) was found to be 0.68, which is lower than Emax estimated for the species using Beverton and Holt yield per recruit analysis. Thompson and Bell prediction model showed that at current exploitation level, the biomass (B) has reduced to 32% of virgin biomass (B0) where as, the spawning stock biomass (SSB) has reduced to 16% of the virgin spawning stock biomass (SSB0). Hence the exploitation level for the species should be reduced by 40% that will ensure the availability of SSB at a relatively safer 30% level to rebuild the stock for long term sustainability of the resource.

Food And Feeding Habits of Two Major Lizardfishes (Family: Synodontidae) Occurring along North-West Coast of India Between Lat. 18°-23°N

Food And Feeding Habits of Two Major Lizardfishes (Family: Synodontidae) Occurring along North-West Coast of India Between Lat. 18°-23°N

Length at first maturity of cobia Rachycentron canadum (Linnaeus, 1766) from north-west coast of India

The length at first maturity of cobia Rachycentron canadum (Linnaeus, 1766) was estimated from 292 specimens collected during exploratory surveys along the north-west coast of India and from fish landing centres in Mumbai, Maharashtra. Length and age at first maturity of male and female were estimated as 63 and 70 cm and 1.5 and 1.75 years respectively.

Trend of gillnet fishery along the Maharashtra coast of India: A case study

In the context of increasing fuel prices in fishing operations, low impact fuel efficient (LIFE) fishing practices such as gillnetting assume significance globally for sustainable development of fisheries. Satpati, which is well known for the dominance of mechanised gillnet fishing is an important marine fishing zone of Maharashtra along the north west coast of India. Considering the relevance of fuel efficient fishing methods, the present study focuses on highlighting the importance of gillnet fishing and to document the several changes that have taken place in the fish catch composition and fishing operations in the gillnet fishery at Satpati during the last few decades. The catch data were collected by fortnightly sampling from the single-day (lobster gillnetting) and multiday (pomfret and seer fish gillnetting) gillnet fishing. Specifications of crafts were recorded in the pre-scheduled questionnaire and by physically sampling the units. The study analysed the catch composition of all the three representative units that revealed a change in the trend of species composition over the years. The contribution of pomfrets to the total marine fish landings of Satpati had reduced from 30% in 1987 to 20% in 2015. This can be mainly attributed to the usage of smaller mesh size and increase in juvenile catch of pomfret over the past few years. In this regard, results of the present study with regard to assessment of the present scenario of the mechanised gillnetter fleet at Satpati would be useful to decision makers for imposing fishing fleet restrictions.

Diversity and distribution of mysids (Crustacea:Mysida) from the northwest coast of India

Diversity and distribution of mysids (Crustacea:Mysida) from the northwest coast of India

An Assessment on Economic Impact of Growth Over Fishing of Commercially Important Marine Ariids Along Mumbai, Northwest Coast of India.

The economic assessment on juvenile landings of four dominant marine catfishes at New Ferry Wharf (NFW) landing centre, Mumbai, Northwest coast of India was carried out during January to December, 2013. The dominant catfishes viz. Nemapteryx caelata (19.7 %), Plicofollis dussumieri (21.5 %), P. tenuispinis (24.8 %) and Osteogeneiosus militaris (27.5 %) together contributing 93% of total marine catfish landings of the state. Among four species, the juvenile landings of N. caelata contribute maximum(93.17 %) followed by P. dussumieri (57.14 %), O. militaris (36.11 %) and P. tenuispinis (21.43 %) with the maximum landing during November to March . The bioeconomic model reveals that if juveniles are allowed to grow up to length at first maturity (Lm); an estimated total annual economic gain will be Rs. 13.15 crores with an estimated biomass gain of 1222 t per annum. The estimated total annual biomass is increased by 2.07 times with an increase in additional revenue by 3.7 times would have been realised. The results of present study suggest that sustainable harvest of these resources would have been yielded maximum economic return to the fishers. With the help of stakeholders participatory approach, management measures such as strict mesh size regulation, effort restriction on bottom trawl up to 50 m depth and awareness campign on catching juveniles and adult in particulat to the oral incubated male ariids, would have been implemented during November to March to avoid growth over fishing.

An Evaluation of Economic Impact on Juvenile Landings of Cephalopods in Mumbai Waters, Northwest Coast of India

Economic assessment of juvenile landings of 5 dominant cephalopods at New Ferry Wharf (NFW) landing centre, Mumbai was carried out during January to December, 2013. Dominant cephalopod fishery recorded include one species of squid, Uroteuthis (P) duvaucelii, three species of cuttlefishes, Sepia elliptica, Sepia pharaonis, Sepiella inermis and a species of octopus, Cistopus indicus together contributing 98% of total cephalopod landings. Estimated total annual economic gain calculated using bioeconomic model was Rs. 33.22 crores with estimated biomass gain of 4995 t per annum, if juveniles are allowed to grow up to length at first maturity (Lm)/Lmean. Among five species, C. indicus contribute maximum with 64.07 % of average juvenile catch followed by U. (P) duvaucelii (26 %), S. elliptica (23.63 %), S. inermis (23.27 %), and S. pharaonis (12.85 %). On these resources, while in S. inermis, both LM equals Lmean indicates breakeven point for the species. The study revealed that peak spawning season of these species coincides with peak juvenile landings which may result in reduction of overall size range thus will lead to loss of fishery in economic as well as ecosystem regime. The study indicates the improvement of harvest biomass by 2.95 times which would result in generating additional revenue to the fishers by a margin of 3.71 times; if juveniles are allowed to grow up to Lm/ Lmean whichever is greater.

Growth, mortality and exploitation of bigeye scad,Selar crumenophthalmusoff Mumbai, north-west coast of India

An investigation was carried out to study the growth, mortality and exploitation of bigeye scad,Selar crumenophthalmusoff the Mumbai coast during September 2008 to August 2009. The von Bertalanffy growth equation was derived asLt= 310 mm [1−exp {−1.4 year−1× (t−(−0.059 year))}] with the growth performance index (ø’) of 3.13. The fishable lifespan of the species was 2+ years in Mumbai waters. Bigeye scad attains total length of 240 and 293 mm during its first and second year of life. The size at first capture (Lc) was estimated as 240 mm (1+ year). The recruitment was continuous and throughout the year with a single pulse during August. Nearly 50% of the recruitment took place during August and September. The total, natural and fishing mortality rates were 4.62, 2.21 and 2.41 year−1, respectively. The estimated exploitation ratio (0.52) was very close to the optimum value of 0.5. Hence, the stock can be considered as optimally over-exploited in Mumbai waters.

Seasonal studies on field cultivation of Kappaphycus alvarezii (Doty) Doty on the northwest coast of India

Cultivation of Kappaphycus alvarezii was carried out at Okha, northwest coast of India, from August 2004 to April 2006, using the raft and net bag methods. Seawater temperature, salinity, nitrate, and phosphate varied seasonally, with average values of 26.51 ± 1.72 °C, 34.23 ± 1.79 ‰, 17.46 ± 8.77 μM L−1, and 1.32 ± 0.78 μM L−1, respectively. After 15, 30, and 45 days of growth, average daily growth rates (DGRs) were 6.87 ± 0.27, 5.99 ± 0.18, and 4.97 ± 0.08 % with corresponding biomass of 292.43 ± 12.06, 629.58 ± 32.56, and 977.98 ± 36.59 g FW plant−1, respectively, for the raft cultivation. In the net bag method, after 15, 30, and 45 days of growth, the mean DGRs were 7.88 ± 0.38, 5.83 ± 0.10, and 4.42 ± 0.14 % with biomass values of 348.98 ± 19.48, 623.28 ± 29.95, and 813.73 ± 52.64 g FW plant−1, respectively. This study confirmed the feasibility of cultivating K. alvarezii on the northwest coast of India.

Reproductive biology of the Indian scad, Decapterus russelli (Ruppell, 1830) from Maharashtra waters, northwest coast of India

The length at which 50% of females of Decapterus russelli attain maturity was estimated at 153 mm. The presence of mature, ripe and spent gonads was observed from June to October and December to April indicating prolonged spawning season. The sex-ratio varied from 1:0.43 in 140-149 mm to 1:1 in 110-119 mm length groups. Month-wise distribution of sex-ratio indicated significant predominance of male at 5% in April, May and November. The absolute fecundity ranged from 29,986 to 1,52,123 eggs. Based on the GSI studies it is inferred that the species has a prolonged spawning season probably falling between December to March and June to October. The relative condition factor value was highest in January which indicates the peak spawning month. Length-wise condition factor of males and females were maximum in the length range of 100-229 mm. In the present study size of ova diameter ranged from 0.01 to 0.97 mm. The species seems to spawn twice in a season and the period between two spawning may not be a long one.