1. Drift Gillnetting for Large Pelagics in the West coast of India with special reference to Tuna
Research Guide
Dr. Saly N.Thomas
Principal Scientist
External Expert
Dr.Leela Edwin
Muhammed Sherief P.S
Research Associate

2. Scope of Research
Changes are observed in gillnet fishing in India over the years , as in the form of introduction of new gear material, mechanization of fishing vessel and net hauling equipment. So a study on the present status and details of fleet structure of gillnet fishing is relevant in this context.
Through large mesh drift gillnetting this study intends to create an understanding on the distribution, abundance, and habitat of tuna and other large pelagics in the west coast of India.
In high sea drift gillnetting, the cost of gear accounts for 44% to 56% of the total investment (Thomas, 2001). So, a study on material substitution of polyamide with new generation gear material and optimized design is necessary
The major problem in drift gillnetting is bycatch, which includes marine mammals, sea turtle, sea birds and non targeted fish species (Boopendranath, 2012). There is a paucity of information on bycatch associated with gillnet fisheries throughout the Indian coast.

3. Objectives
To understand the present status of large mesh tuna drift gill netting of west coast of India
To optimise the design of cost effective drift gillnetting through material substitution.
To analyze the technical and economic efficiency of the high sea drift gillnetters of the west coast of India
To assess the bycatch from gillnetting on quantitative and qualitative basis

4. Methodology:
The current status of large mesh drift gillnetting operations in the west coast of India will be investigated by direct observation and by interviewing the fishers using questionnaires (Sree Krishna & Shenoy (2001) and Thomas & Hridayanathan (2002). Design documentation as per Nedelec (1975).
Experimental fishing with design modified and material substituted gillnets will be conducted to compare the catching efficiency and profitability (Thomas, 2001).
Bycatch issues in drift gillnetting will be estimated through onboard observation and direct interview using structured questionnaire (Yousuf et al., 2008 )

5. Introduction
Tuna and tuna-like fishes are important both from global demand and economic view points.
Globally, in terms of fishing gear, 63% of the catch is made by purse seining, followed by longline (12%), pole and line (10%), gillnets (4%) and miscellaneous gears (11%)( ISSF, 2015).
In India, major share of the tuna catch realized was from gillnets (51.6%) followed by purse seine (19.9%), hooks and line (12.2%) and small quantities (12.1%) (CMFRI, 2014).
Global drift gillnet operation
Reference
Indian ocean, Atlantic, Pacific Mediterranean sea countries
Northridge, 1991; Abdussamad, 2012; Satheesh Kumar and Pillai, 2014
Algeria, Morocco, Spain, France, Italy, Malta, Greece, Turkey, Pakistan, Indonesia, India, Iran, Oman and Somalia
EJF, 2007; Moazzam, 2012; IOTC, 2013

6. Introduction
Drifting gillnets are set close to the surface or below it with the use of floats. These nets drift freely with the current, either separately or with the boat to which they are attached (Nédélec and Prado, 1990)

7. Design of typical tuna drift gillnet

8. Drift gillnetting in India
Indian tuna fishery comprises coastal fishery and oceanic fishery (Somvanshi et al., 1998); constituted by motorised and mechanised sectors (Thomas,2010).
Total numbers of gillnetters in India increased from 2,362 in 1980 to 20,257 in 2010 (CMFRI, 1981, 2012).
During 80’s the length of gillnets operated varied from m (Silas et al., 1984; Boopendranath and Hameed, 2013); during 1990s around 2150 m (Vijayan et al., 1993; Ganga et al., 2008; Thomas, 2010) ; during , m (Thomas, 2010); while during 2014 upto m (Edwin et al., 2014).
Motorised gillnet sector comprise of wooden ,Fibre Reinforced Plastic(FRP) and marine ply wood canoes( m LOA fitted with 15 to 25 hp OBM (Madhu et al., 2002; Ganga and Pillai, 2006; Thomas, 2010).
Presently, mechanized gillnetters targeting tuna are of 8 to 19 m LOA fitted with 24 to 193 hp engines (Edwin et al, 2014).

9. Material of construction
Till late 1950s, hemp and cotton were used for gillnets which was later replaced by nylon multifilament twine (Vijayan et al., 1993).
In early 90s, the nylon monofilament was introduced and by 2000, monofilament almost completely replaced nylon multifilament in the gillnet sector in many states of India (Vijayan et al., 1993; Rao et al., 1994; Pravin et al., 1998; Pravin and Ramesan, 2000; Thomas, 2001; Thomas et al., 2005; Chaidee et al., 2007).
Gill nets for tuna and other large pelagic fishes are mainly made of PA multifilament of 2l0dx6x3 to 210dx12x3 netting (Thomas, 2010).
HDPE yarn and HDPE twine was found to be on par with nylon for large pelagics (Pillai et al .,1989; Thomas &Hridyanathan, 2003; Pravin et al., 2009).
In Gujarat, Andhra Pradesh and Tamil Nadu, HDPE is used as drift gillnet material along with nylon(Rao et al.,2002).
Recently, materials like sapphire a highly modified form of PE was found used for large mesh gillnet in certain pockets of Gujarat (Sherief et al.,2014).

10. Mesh size Mesh size Target fish Reference 60 -115 mm
Tuna, seerfish, shark
Jude et al., 2002
237 mm
Tuna
Hossini , 2003 mm
Neethi selvam and Jude , 2006 mm
Tuna , swordfish,shark
145 mm
Mehran et al., 2009

11. Operational parameters
Up to 1990s, mechanized drift gillnetters carried out single day fishing trips and started switching over to two and three day trips (Silas et al.,1984, Boopendranath and Hameed, 2013).
By late 90s , trips of one week and two weeks were common (Thomas , 2001).
By 2010, mechanised gillnetters were undertaking multiday fishing extending up to 30 days (Thomas, 2010) and now this is extended up to 45 days (Edwin et al., 2014).
Gillnet cum longlining is a very common practice contributing to more than 75 % of the total tuna fishing in the country (Balasubramaniam, 2000).
Operational parameters

12. Operational parameters
High sea drift gillnetters operated by Tamil Nadu fishermen operate up to depth of 1000 m for catching tunas, sharks, skates, rays and chimaeras (Joshi et al., 2008; Akhilesh et al., 2009)
Recently net haulers were found used in large mechanised gillnetters operated by Tamil Nadu fishermen (Edwin et al., 2014).
In gillnetter cum longliners, hydraulic line haulers are fitted behind the wheel house (Edwin et al., 2014).

13. Catch composition
From 2000 onwards, the species composition of drift gillnets was diverse in nature due to the expansion of fishing ground to oceanic and deeper waters (Akhilesh et al., 2012).
Catch of drift gillnet for large pelagics comprised mainly tuna, swordfish, sail fish, seer fish , shark etc .
However, a detailed information on catch composition and size statistics is lacking (Yousuf et al ., 2008)

14. Techno-economic feasibility
In the Indian context, techno-economic aspects of purse seine was studied by Mukundan and Hakkim (1980); Verghese (1994); Panikkar et al. (1993) and Shibu (1999) and of trawling by Iyer et al., (1985); Devaraj Smitha (1988); John (1996) and Shibu (1999).
Economic aspects of marine gillnets operated in Kerala were studied by Iyer et al., (1993), Shibu (1999), Panikker et al., (1993).
Techno economic efficiency of gillnets along Kerala coast was reported by Kurien (1982), Thomas (2001).
In high sea drift gillnetting, the cost of gear is accounted for 44% to 56% of the total investment (Thomas, 2001).
One way of reducing the cost of the gear is by substituting the material with a less costly but durable material.

15. Bycatch problem Bycatch occurs in virtually all fisheries.
Bycatch is the unintended catch in a fishing operation of species other than the target species, or individuals of the target species that are of undesirable size. Bycatch can either be discarded or landed (ISSF,2015).
Though bycatch was considered as a problem mainly in the trawl sector, wide spread use of large scale drift gillnets resulted this, applicable to this sector also (Northridge, 1991).
In terms of important bycatch issues in the tuna fisheries of the Indian Ocean, the catch of marine mammals and sea turtles is often mentioned and there is some concern about shark bycatch, mainly in the gillnet fisheries .
Tuna gillnet bycatch mainly consists of Scombroids followed by barracuda, dolphin fish, thresher shark, silky shark, other requiem sharks and black marlin, striped marlin, mako, mantas and Indo-Pacific sailfish (Moazzam, 2011;2012).

16. Gillnet by catch
Species
Reports
Cetaceans
Cockcroft &Krohn, 1994; Perrin et al., 1994;Archer et al., 2001; Wise et al., 2001; Read et al., 2006.
Kumarran (2012), Jayaparkash et al. (1995), Mohan (1985) Pillai and Chandrangathan (1990), Silas et al. (1984) and Yousufet al. (2008 )
Lal Mohan, 1994, Yousuf et al., 2008)
Sea bird
Zydelis et al. 2009; Croxall et al, 2012; Løkkeborg, 2008, Merkel 2004, Christensen-Dalsgaard et al. 2008, , Žydelis et al,2009) Waugh et al., 2011
Turtle
Rajagopalan et al., 1996;2002; MARG, 2012; Lobo, 2007; Bhoopathy and Karunakaran , 2003,
Shark
Clarke et al. 2007, Walker 1998, Kelleher 2005, Fowler et al. 2005, Bonfil 1994; Stevens et al.,2000; FAO 2009; Akhilesh et al., 2011

17. Target S p e c i s B Y C A T h S p e c i Group Species Species
Tropical tunas
Yellowfin tuna
Bigeye tuna
Skipjack tuna
Temperate tunas
Albacore
Southern bluefin tuna (CCSBT)
Bilfish
Swordfish
Black marlin
Blue marlin
Striped marlin
Indo-Pacific sailfish
Neritic tunas
Longtail tuna
Frigate tuna
Bullet tuna
Kawakawa
Seerfish
Narrow-barred Spanish mackerel
Indo-Pacific king mackerel B Y C A T h S p e c i
Species
Sharks and rays
Highly migratory species of sharks (e.g. blue, makos, oc. whitetip, silky, thresher, porbeagle) and rays (e.g. manta rays, pelagic stingrays)
Marine turtles
Green, hawksbill, leatherback, loggerhead, olive ridley, flatback
Seabirds
Several species of albatross, petrels and shearwaters
Marine mammals
Several species of toothed and baleen whales
Other finfish
Other tuna species and other non- targeted, associated and dependent species

18. Conclusion
Only few researchers have addressed drift gillnet fishing for large pelagics in Indian waters.
Coastal tunas have been exploited from Indian waters both as targeted catch and as incidental bycatch since very long and the production reached very close to their estimated potential.
Changes are observed in gillnet fishing in India over the years, as in the form of introduction of new gear material, mechanization of fishing vessel and net hauling equipment.
As the volume of gear used is becoming larger year after year, the investment on gear is also increasing. Material substitution of polyamide with new generation gear material and optimized design is necessary to reduce the cost without compromising on the catching efficiency.
There is a paucity of information on bycatch associated with drift gillnet fisheries throughout the Indian coast
There is a need to assess the level of bycatch quantitatively and qualitatively .

19. Progress of work
Details of large mesh drift gillnet systems operated along the west coast of India were collected and compiled.
New generation fishing gear materials procured and material properties being tested.
Experimental gillnets using new generation material designed.
Experimental gillnet along with control gear fabricated and arrangements being made for experimental trials.

20. Thanking you
for your attention