Bi l di it d di t ib ti i Bivalve diversity and distribution in relation to salinity

Boominathan, M.

Subash Chandran, M.D.

Ramachandra, T.V.Energy & Wetlands Research Group, CES, IISc, Bangalore

IntroductionIntroduction

• An estuary is a semi-enclosed coastal body of An estuary is a semi enclosed coastal body of water having a free connection with the open sea and within which the sea-water is measurably diluted with fresh water deriving from land drainage (Pritchard, 1963).

• In estuaries, salinity levels – highest near the mouth– lowest at upstream (oceanservice.noaa.gov).

Estuarine organisms ha e different tolerances • Estuarine organisms have different tolerances and responses to salinity changes.

• Many bottom-dwelling animals, like bivalves, can tolerate some change in salinitycan tolerate some change in salinity.

• But salinities outside an acceptable range will • But salinities outside an acceptable range will negatively affect their growth and reproduction, and ultimately, their survival (Russell-Hunter, and ultimately, their survival (Russell Hunter, 1983; oceanservice.noaa.gov).

A h hi i i id ( b 6 k ) • Aghanashini estuary is wide (about 2 to 6 km) and heterogeneous in its structure.

• It is well known for its bivalve diversity (Bhat, 2003) 2003)

H li it i i t t d t i i • Hence, salinity is an important determining factor of bivalves this paper discuss about the salinity preference of edible bivalvessalinity preference of edible bivalves.

Objectives

To see the edible bivalves diversity and To see the edible bivalves diversity and distribution.

To understand the habitat preference of those speciesthose species.

To examine the salinity preference of those bivalves.

Study areaStudy area

Aghanashini estuary

Uttara Kannada Dist.

Salinity sampling pointsy p g pBivalve sampling points

MethodsBivalve diversity and distribution

edible bivalve shells were collected from eight d b b o d o glocalities

shells were identified in the laboratory.y

Salinity Salinity surface water samples were collected from 21 station at high-tide periodstation at high-tide period

salinity were analysed in the laboratory using electrode probeelectrode probe.

l d di iResults and discussion

Clam : diversity and habitat

Paphia malabarica Villorita cyprinoides Shallow water

M dfl t / d b tt / i t tid lMudflat / sandy bottom / intertidal

Katelysia opima Meretrix meretrix M. casta Arca granosa

Rocky areas

Oyster : Crassostrea sp.Oyster : Crassostrea sp.

Mussel : Perna viridis

Salinity preferences Salinity preferences Full seawater (38 to 40 ppt)

32 ppt to full seawater

Freshwater to 30 ppt3 pp

Almost same salinity values were obtained by Bhat, 2003 in his hydrological Studies of A h hi i E t Aghanashini Estuary.

M di i ( f i ) b d Most diversity (seven sp. out of nine) observed near the river mouth (38 to 40 ppt salinity).

Bivalve diversity was more in mud flat (four sp.) than other habitatsthan other habitats.

Conclusion

• In this study salinity was measured in the summer month May at high-tide period.

• Hence, it can be consider as the upper limit of li i f f h bi lsalinity preference of these bivalves.

• To see the lower limit of salinity preference monsoon sample is needed.

• To see the complete diversity of bivalves (edible d dibl ) tit ti lit ti and non edible) quantitative or qualitative

sampling is necessary.

h kThank you

AcknowledgementAcknowledgement

• Dr Prakash Mesta, Dr Nayak, V N, and Dr Dr Prakash Mesta, Dr Nayak, V N, and Dr Kusuma Neelakantan, Dept. of Marine Biology, Karwar.

• Ravish, and EWRG members. ,

• The Ministry of Environment and Forests.e s y o o e a d o es s