ISSN 0254-380 X No. 192 June, 2007 Mar. Fish. Infor. Serv., T&E Ser., No. 192, 2007 21

View metadata, citation and similar papers at core.ac.uk brought to you by CORE

provided by CMFRI Digital Repository Mar. Fish. Infor. Serv., T&E Ser., No. 192, 2007 6

(11) Dugong dugon (Dugong)

Sl. Sequence definition of the individuals GenBank No. Accession No. 1 Dugong dugon isolate M4 mitochondrial control region, EF057439 partial sequence Dugong dugon isolate M4 Cytochrome b (cytb) gene, partial EF-057440 cds; mitochondrial verification of trade records and for identifying tion. The following table depicts 63 mtDNA ambiguous beach-cast specimens. sequences from 40 individuals of 11 species hitherto deposited by the CMFRI team in Against this background, CMFRI has initiated GenBank, details of which can be accessed mitochondrial DNA sequencing of cetaceans from www.ncbi.nlm.nih.gov/. using the and dugong from the Indian seas under a accession number given in the third column. project sponsored by the Ministry of Earth Sciences, with a view to accurately identify Prepared by : P. Jayasankar, B. Anoop, M. the species even from a piece of skin, by Rajagopalan, E. Vivekanandan, P.K. mtDNA PCR and sequencing of specific loci, Krishnakumar, P L. Kumaran, P. Reynold, such as control region and cytochrome b A.K. Anoop, K.M.M. Yousuf and V.V. Afsal, gene, followed by phylogenetic reconstruc- CMFRI, .

1238 Bivalve resources and its exploitation in Malabar

The Malabar region of (, collected by handpicking / scoop nets during , Mahe, Kasargod) has significant low tides, while the edible oyster is chipped bivalve resources contributing to subsistence out with the help of a knife. The occurrence fisheries of the local population. Clams and of clams and oysters in different estuaries of oysters form the major resources in the Malabar region is listed in Table 1 below. estuaries and backwaters. The clams, Meretrix casta, Meretrix meretrix, Villorita Exploitation of clams and oysters is highly cyprinoides, Paphia malabarica and the seasonal and the production fluctuates from edible oyster, Crassostrea madrasensis form year to year. The total bivalve production the major exploited bivalve resources of from Kozhikode to Kannur region was commercial significance. The clams are mainly estimated at 15.682 t during 2006. The total Mar. Fish. Infor. Serv., T&E Ser., No. 192, 2007 7

Table 1: Distribution of clams and oysters in different regions and estuaries of Malabar Region Estuary Resource Kozhikode Meretrix casta, Villorita cyprinoides, Crassostrea madrasensis Moorad Meretrix casta, M. meretrix*, Villorita cyprinoides, Crassostrea madrasensis, Saccostrea cucculata Chaliyar Meretrix casta, Villorita cyprinoides, Crassostrea madrasensis Mahe Mahe Meretrix casta, Villorita cyprinoides, Crassostrea madrasensis Kannur Paphia malabarica, Anadara granosa*, Crassostrea madrasensis Valapattinam Meretrix casta, Villorita cyprinoides, Paphia malabarica, Crassostrea madrasensis Kasargod Padanne Meretrix casta, Villorita cyprinoides, Paphia malabarica Chandragiri Meretrix casta, Villorita cyprinoides, Paphia malabarica, Crassostrea madrasensis *Very sparse population bivalve production increased by 25% (3932 t) 5% to the total bivalve production while over the previous year (Fig. 1). This includes P. malabarica contributes only 0.2 %, and the green mussel Perna viridis from the C. madrasensis 0.3%. The bivalve coastal beds, constituting nearly 65% of the exploitation during 2005-2006 in major total bivalve production. M. casta contributes estuaries is presented in Fig. 2.

1000 C. madrasensis P. malabarica P viridis Total 16000 2005 2006 900 V. cyprinoides M. casta 14000 800

12000 700 600 10000 500 8000 400

6000 (t) Production Production (t) Production 300 4000 200 M casta 100 2000 P malabarica V cyprinoides C madrasensis 0 0 2005 2006 2005 2006 2005 2006 2005 2006 2005 2006 Chaliyar Dharmadom Mahe Moorad Thorai Fig. 1. Bivalve production : Malabar Fig. 2. Clam/oyster production in major 2005-2006 estuaries: 2005-06 Mar. Fish. Infor. Serv., T&E Ser., No. 192, 2007 8

Meretrix casta: M. casta is exploited from 2001 to 2006 was 163 t with an average Korapuzha, Moorad, Chaliyar, Mahe and production of 27 t. The total effort during the Valapattinam estuaries in Kozhikode and period was 7328 with an average effort of Kannur regions. It contributes nearly 10% to 1221. The CPUE was 22 kg. The fishery the total bivalve production. It is exploited for fluctuated between the years. Maximum meat as well as shell. Significant quantities are landings were recorded in 2002 at 69 t landed from Moorad and Chaliyar estuaries. followed by 2004 at 39 t. The effort increased The total production of M. casta during 2000 several folds in 2002 and 2004 (Fig. 4). Peak to 2006 was 5915 t, with an average annual fishing occurs during November to May. production of 845 t. The total effort during The clams are sold at the rate of Rs. 4 /kg the period was 46460 (persons) with an shell-on. average effort of 6637. The CPUE was 4000 55 127 kg. The fishery fluctuated between the Total Catch (T) 50 3500 Effort (No. of persons) C/E (Kg) 45 years. Maximum landings were recorded in 3000 40 2500 35 C 2003 at 1954 t followed by 2001 at 1690 t. / 30 E 2000 The effort increased several folds during 25 (K g) 1500 20 Total Catch (t) Catch Total 2002-2003 (Fig. 3). Peak fishing occurs 15

Effort (No of Persons) of (No Effort 1000 10 500 during November to May. The clams are sold 5 0 0 at the rate of Rs. 2 /Kg shell-on. 2001 2002 2003 2004 2005 2006 Years

16000 350 Fig. 4. Production of Paphia malabarica, Total Catch (T) 14000 Effort (No. of persons) 300 C/E (Kg) Dharmadom estuary, 2001-06 12000 250 C 10000 / 200 E Villorita cyprinoides: V. cyprinoides is 8000 150 (K 6000 g) exploited from Korapuzha, Moorad, Chaliyar, 100 (t) Catch Total 4000 Effort (No of Persons) of (No Effort Mahe, Valapattinam, Padanne and 2000 50 Chandragiri. It contributes about 5% to the 0 0 2000 2001 2002 2003 2004 2005 2006 total bivalve production. It is exploited for Years meat and shell. The total production of Fig. 3. Production of Meretrix casta, Moorad estuary, 2000-06 V. cyprinoides during 2004 to 2006 was 1808 t with an average production of 603 t. Paphia malabarica: P. malabarica is The total effort during the period was 14664 exploited from Dharmadom and Valapattinam. with an average effort of 4888. The CPUE It contributes about 0.1 % to the total bivalve was 123 kg. Peak fishing occurs during production. It is exploited for meat and shell. January to May. The clams are sold at the The total production of P. malabarica during rate of Rs. 1.5/kg shell -on. Mar. Fish. Infor. Serv., T&E Ser., No. 192, 2007 9

Crassostrea madrasensis: C. madrasensis 7000 140 Total Catch (T) Effort (No. of persons) 120 beds occur in Korapuzha, Moorad, Chaliyar, 6000 C/E (Kg) 5000 100 Mahe and Dharmadom estuaries. However, C / exploitation is prevalent only in Dharmadom. 4000 80 E 60 (K 3000 g) In all other estuaries, exploitation is very (t) Catch Total 2000 40 Effort (No. of Persons) of (No. Effort meager, only to meet the local household 1000 20 requirements. The total production of 0 0 2001 2002 2003 2004 2005 2006 C. madrasensis during 2001 to 2006 was Years Fig. 5. Production of Crassostrea madra- 2153 t, with an average annual production of sensis, Dharmadom estuary, 2001-06 359 t. The total effort during the period was 20237 with an average effort of 3373. The The exploitation of clam and oyster resources CPUE was 106 kg. The fishery fluctuated form a source of subsistence level livelihood between the years. Maximum landings were option for the local pickers. No management recorded in 2002 at 718 t. The effort practices are in vogue. Several factors affect increased several folds during the years the spat fall and this contributes to the although production declined over the years seasonality of the bivalve fishery. (Fig. 5). Peak fishing occurs during January Prepared by : P. Laxmilatha. M.P. Sivadasan to May. The oyster meat is sold at the rate of and V.G. Surendranathan, Calicut Research Rs. 50 /kg. Centre of CMFRI, Calicut

1239 Pollution from fishmeal plant discharge at Mukka beach, north of

Effluents from various industries are major removed by simple methods. The effluents source of pollutants in the coastal areas. The from seafood processing (such as shrimp type and magnitude of pollution and the impact processing) units in most of the places are of on coastal environment depends on the limited quantity and directly discharged into physical and chemical characteristics of the the neighbouring water bodies. Apart from effluent, the mode of discharge and the raising the BOD in the immediate vicinity, hydrodynamics of the receiving body. While these limited effluents generally do not cause several chemical manufacturing industries any severe damage to the system. However, produce toxic effluents which need special the waste from fishmeal plants which contain treatment and disposal, the process the body fluids of fish, often cause severe wastewater from fish/food processing units pollution which may even lead to deterioration have high organic content which can be of coastal beaches.