A Study on the by-Catch Assessment of Mature Sharks (Superorder: Selachimorpha) in Commercial Fishing at Thoothukudi District Fish Landing Centers, Tamil Nadu

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A Study on the by-Catch Assessment of Mature Sharks (Superorder: Selachimorpha) in Commercial Fishing at Thoothukudi District Fish Landing Centers, Tamil Nadu

K. Ganesp

Ph.D., Zoology Research Scholar, Reg.No.18112232191021.

V. O. Chidambaram College, Thoothukudi. Affiliation of Manonmaniam Sundaranar University,

Abishekapatti, Tirunelveli, Tamil Nadu, India.

Dr. B. Geetha2 Associate Professor, Department of Zoology,

V. O. Chidambaram College, Thoothukudi. Affiliation of Manonmaniam Sundaranar University,

Abishekapatti, Tirunelveli, Tamil Nadu, India.

Abstract:- Sharks and other chondrichthyans are a relatively conserved group of shes that have successfully functioned in diverse marine ecosystems for over 400 million years and other chondrichthyans are a relatively conserved group of shes that have successfully Bycatch is the accidental capture of non-targeted species or undesirable size ranges of the target species by non-selective shing gear. Shark in particular plays an important role in structuring marine communities by inuencing mortality rates and behavior of mesoconsumers and other organisms. The life history of these shes is characterized by late maturity, long life spans, long gestation periods, and few well developed offspring. Indeed, globally shark populations are in decline as a result of a variety of stressors and threats including shing mortality arising from targeted harvest and incidental capture (i.e., bycatch). From the 21 species of shark monitored by the International Union for the Conservation of Nature (IUCN), 27.27 % were reported to be Near Threatened, 22.72 % Vulnerable, 6.25 % Endangered, and 5.68 % Critically Endangered. This means that approximately 62 % of the total shark species are facing major conservation threats.

Keywords: By-catch, Elasmobranchs, Assessment, Sharks, Fishing Gears.

INTRODUCTION:

Overfishing represents the greatest threat to marine fish stocks globally and substantial research has focused on better understanding the vulnerabilities and resilience of marine species to sustained fishing. Modeling and ranking the vulnerabilities of dissimilar species to fisheries capture can provide insight into how fishery-related stressors affect ecologically/biologically similar or different species as well as provide a mechanism for prioritizing species for conservation actions. Elasmobranchs are particularly vulnerable to overfishing due to their relatively low reproductive output and low potential for population recovery compared to most Several elasmobranchs are experiencing drastic population declines across their range. While many shark species are targeted for the global shark fin trade or otherwise retained for consumption elasmobranchs are also unintentionally caught as bycatch in many fisheries, and this catch can often exceed that of the actual targeted species. Bycatch is often

discarded regardless of their at-vessel status (live, injured or dead), and is poorly reported in some fishery records making it difficult to assess impacts. Additionally, management regulations often require that bycatch of threatened species be released to promote their conservation. However, if fishes are dead upon gear retrieval then such practices can be futile for conservation efforts. However, understanding the at-vessel status of individuals caught as bycatch and modeling their survival in light of biological, environmental, and operational variables can provide insights into the underlying mechanisms driving mortality, thus informing which aspects of a fishery might be modified to mitigate lethal effects of capture on a species-specific basis Longline fishing provides one of the largest sources of fisheries interactions with sharks, and it is well known that species with limited biological productivity are among the most vulnerable to many, if not all forms of fishing mortality, including bycatch. Previous studies describing the observational at-vessel survival rates of certain shark species in both pelagic and bottom longline fisheries have documented a wide range of estimated survival rates among species. This work has provided a strong foundation to begin asking additional questions about how bycatch affects the survival of shark species; specifically, assessing the potential influences of operational, environmental and biological variables of the fishery under investigation. For example, pelagic longline fisheries often switch between fishery targets (i.e., tuna versus swordfish), thereby altering environmental (time of day) and operational aspects of the fishery. However, it is unclear if and how these operational differences affect the survival of sharks captured as bycatch. Many shark species have global distributions and are caught incidentally in different types of fisheries. Over the last two decades, shark populations have declined tremendously, with one of the leading causes of this decline bycatch in primarily teleost fisheries. Bycatch occurs throughout the worlds fisheries, but is not well documented in terms of species composition and numbers of each species captured. Information on shark bycatch is

spread through the primary and grey literature, but has not been compiled in summary to date.

REVIEW OF THE LITERATURE:

Sharks have typically been exploited as a by-catch of commercial fisheries targeting more valuable bony fishes, especially tuna and billfish (ICCAT, 2005). In many countries, shark by-catch is partially or primarily retained for the fin, liver oil, teeth and food trade. But even where living sharks are released at sea because they are considered unwanted catch, post-release mortality rates can exceed 18 per cent for some species (Abdussamad,E.M., et al., 2006). In the North-West Atlantic, blue shark by-catch from an international pelagic long line fleet outnumbers the target swordfish catch by about 3:1, resulting in an annual post-release blue shark mortality of ~20,000 mt (Agnew,

D.J et al., 1999). Similar calculations of capture and post- release mortality of released sharks, using conservative mortality estimates for all shark species, suggest total shark mortalities of non-landed sharks of about 34,000 mt per year (Ajmal Khan,S et al., 2005). Elasmobranchs generally called cartilaginous fishes include sharks, rays and skates. The body is disc shaped and almost round or oval in rays and skates. Placoid scales are seen in the skin of sharks but rays have naked body. The gill slits are found in ventral side of the rays and skates. Spiracles are usually present. In India, taxonomy and morphology of elasmobranch were studied only by few researchers. (Haneef, F et.al. 1999) reported that the teeth are important in the fossil record of sharks and exhibit much variation between taxa. (Ganesh,K. and B.Geetha et.al.,2017) studied the large scale exploitation of sacred chank, X. pyrum using modified trawl net (chanku madi) along Rameshwaram coast and its probable adverse impacts. Turbinella pyrum sp and Turbo sp resources displayed a declining trend in catch indicating considerable overfishing in Andaman waters (Abrego, F.M.C.,A.T. Granados. and

F.F. Andolais, 1994). The periodical sweeping of foot ropes with sinker chains of trawl nets appeared to cause severe damage to the egg capsules thus bringing down the recruitment of the chanks due to high mortality rate at the young stage in Gulf of Mannar (Nazerath Nisha, Ganesh,K. and B.Geetha, et.al., 2018). Juvenile sharks are caught in large numbers in purse seine and trawl fisheries, contributing to long-term declines in populations that may not be immediately apparent of Tuticorin in Gulf of Mannar (Ranjiga njali,A. and Ganesh,K. and B.Geetha, et.al, 2018). The fishing for chanks should be banned for

three months (January to march) every year in order to conserves the egg capsules and baby chanks. Murugesan,V. Ganesh,K. and B.Geetha et al., (2019) Elasmobranch bycatch in fisheries around the world has become one of the main sources of population declines. Muthuraman,A. Ganesh,K. and B.Geetha.2019. et.al. (2019) reported a method of processing and preservation of prawn pickle. Thomas, P.K., et al., (2002) observed the levels of trimethylamine oxide and its derivatives in fish and shellfish.

MATERIALS AND METHODS:

The present study on shark by-catch assessment data derived from the pelagic longline fishery in the Gulf of Mannar coastal at Thoothukudi district fish landing centers

i.e. Tuticorin, Threshpuram, Tharuvaikulam, Vembar, Vellapatti . Selected five fish landing centers was carried out for a period of January 2018 to March 2019. Note the measure of the length and weight of only mature sharks. Total by-catch was also estimated while every landing centre has done at the fish auction centers. Documenting sharks in specific regions and understanding their taxonomy and diversity in particular ecosystems are very important for conservation and management of these decreasing resources.

RESULTS:

Mature sharks in thoothukudi fishing harbor totally forty seven, Threshpuram is fifty five, Tharuvaikulam is fifty eight, Vembar is fifty one and Vellapatti is forty five (Table-1). From the 21 species of shark monitored by the International Union for the Conservation of Nature (IUCN), 27.27 % were reported to be Near Threatened,

    1. % Vulnerable, 6.25 % Endangered, and 5.68 % Critically Endangered. This means that approximately 62

      % of the total shark species are facing major conservation threats (Fig.1 to 5). The main motivation of shark catching is for their fins. Millions of sharks were killed every year for their fin soup. Indian Government has banned the sharks catch (only for their fins), however, it is illegally exported to Asian countries viz. China, Singapore, Thailand, Malasia and Hongkong for their festivals and functions. The Central Marine Fisheries Research Institute (CMFRI) and Fishery Survey of India (FSI) should serve as the nodal agencies for assimilation of fishery dependent and fishery independent data, the former through its extensive programme of fisheries resource assessment directly from landing centres along the Indian coastal Management.

      Table 1 Number of Mature sharks species of five landing centers

      Scientific Name

      Tuticorin

      Threshpuram

      Tharuvaikulam

      Vembar

      Vellapatti

      Carcharhinus Milberti

      6

      0

      0

      0

      0

      Carcharhinus Plumbeus

      9

      3

      0

      0

      0

      Carcharhinus Limbatus

      0

      9

      6

      0

      0

      Carcharhinus amblyhynchus

      7

      3

      0

      0

      0

      Carcharhinus Melanopterus

      0

      3

      0

      8

      7

      Carcharhinus Hemioden

      4

      4

      7

      0

      7

      Carcharhinus Obscurus

      0

      0

      0

      0

      8

      Carcharhinus Falcifomis

      0

      0

      0

      0

      7

      CarcharhinusTaurus

      0

      0

      0

      4

      4

      Carcharhinus Indicum

      6

      3

      3

      0

      3

      Carcharhinus Macrostoma

      0

      0

      0

      0

      3

      Alopias Pelagicus

      0

      2

      6

      7

      0

      Alopias vulpinus

      0

      0

      0

      5

      0

      Alopias Superciliosus

      0

      2

      0

      4

      0

      Rhizoprionodon Acutus

      6

      0

      3

      0

      0

      Rhizoprionodon Oligolinx

      0

      0

      0

      7

      0

      Sphyrna Lewini

      0

      8

      4

      0

      0

      Sphyrna Zygaena

      0

      5

      4

      0

      0

      Rhina Ancylostoma

      0

      5

      6

      8

      0

      Squatina Albipuncfata

      5

      5

      9

      2

      0

      Stegostoma rasctatum

      0

      0

      6

      0

      6

      Echinorhinus brucus

      4

      0

      4

      0

      0

      Eulamia Spallazani

      0

      0

      0

      6

      0

      Eridacnis radcliffei

      0

      3

      0

      0

      0

      Total

      47

      55

      58

      51

      45

      Fig.1 to 5 By-catch Assessment of Mature Sharks in Fish Landing Centre wise

      Threshpuram Fishing Centre

      Carcharhinus Milberti

      Carcharhinus Plumbeus

      Carcharhinus Limbatus

      Carcharhinus amblyhynchus

      Carcharhinus Melanopterus

      Carcharhinus Hemioden

      Carcharhinus Obscurus

      Carcharhinus Falcifomis

      CarcharhinusTaurus

      Thoothukudi Fishing Centre

      Carcharhinus Milberti

      Carcharhinus Plumbeus

      Carcharhinus Limbatus

      Carcharhinus amblyhynchus

      Carcharhinus Melanopterus

      Carcharhinus Hemioden

      Carcharhinus Obscurus

      Carcharhinus Falcifomis

      Tharuvaikulam Fishing Centre

      Carcharhinus Milberti

      Carcharhinus Plumbeus

      Carcharhinus Limbatus

      Carcharhinus amblyhynchus

      Carcharhinus Melanopterus

      Carcharhinus Hemioden

      Carcharhinus Obscurus

      Carcharhinus Falcifomis

      Vembar Fishing Centre

      Carcharhinus Milberti Carcharhinus Plumbeus Carcharhinus Limbatus Carcharhinus amblyhynchus Carcharhinus Melanopterus Carcharhinus Hemioden Carcharhinus Obscurus Carcharhinus Falcifomis CarcharhinusTaurus

      Vellapatti Fishing Centre

      Carcharhinus Milberti

      Carcharhinus Plumbeus

      Carcharhinus Limbatus

      Carcharhinus amblyhynchus

      Carcharhinus elanopterus

      Carcharhinus Hemioden

      Carcharhinus Obscurus

      CONCLUSION:

      Management of sharks varies greatly between countries and is non-existent, of low priority, or in the early stages of development in many. Additionally, no regional fishery management organizations (RFMOs), international organizations that manage the fishing of high seas stocks, have developed management plans for sharks or set catch limits. Some RFMOs have, however, implemented mandatory species-specific reporting of shark landings, placed bans on finning, called for reductions in fishing mortality, encouraged the live release of sharks or prohibited the retention of certain species. Finning, the practice of removing and retaining shark fins while discarding the remainder of the carcass at sea is widespread. Protective shark finning policies, such as banning finning or the sale and possession of fins, have been shown to reduce the mortality associated with this practice in fisheries that are heavily monitored through surveillance and enforcement or in areas where there is little to no market for shark meat and therefore no incentive to fish for sharks.

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