S I N. UNNIKRISHNAN NAIR. Craft & Gear division, Cochin-11

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1 BSE s E f S I c COC I E N. UNNIKRISHNAN NAIR Centre/ Institute of Fisheries Technology, Craft & Gear division, Cochin-11 The occurrence of the: 4 scies of bryozoans under study showed that Electra crustulenta PALLAS and Victorella avida KENT are brackish water forms, Electra b2!1ga!ensis stoliczka and Schizoorella Cochinensis Menon and Nair are tyical marine forms. It is interetlg to note the seasonal succession of these secies in Cochin Harbour corresond to the distribution of salinity in this area. INTRODUCTION Scheer ( 1945) brought to light th; imortant ecological role of the bryozoan community in tlle sequence of settlement of the marin sedentary organisms. Kuriyan (195, 1952), Daniel (1954), Iyengar et a1 ( 1957) Ganaathi et al (1958), Antony Raja (1959). Balas:.1bramanyan et. al (1963), Nair (1971) observed fouling bryozoans in their studies on fouling orgatlisms. However, systematic studies on Indian bryozoans were initiated by Menon (1967) and Nair {1967, 1969, J97J., 197b, 197c & 1971). While conductiig studies on fouling organisms at Cochin Harbour (lat. 9o 58 1 N, lor1g. 76 l7'e) the author had oortunities to observe the settlement of four scies of bryozoans. These animals exhibited quite interesting characteristics m their settlement. MATERIAL AND METHODS The bryozoans were allowed to freely settle on smooth glass anels 5 X 1 X 3 mm) arranged on to a grooved wooden rack and exosed subtidally one foot below low waterline from the Institute test VoL X No site (Balasubramanyan and Menon, The anels were examined eriodically and the intensity of settlement noted by counting the riumber of colonies. Hydrological conditions such as surface water temerature and salinity were recorded (Table-1). Based on the distribution of salinity, the year was divided into re-monsoon (Jan - Aril) monsoon (May - August and ost monsoon (Setember - December). DISCUSSION E!Pctra Crustulanta PALLAS, Electra bengalensis STOUCZKA, Schizoorella cochinensis MENON & NAIR 1971, Victorella avida KENT were the four secies of fouling bryozoans found settling on anels during the various eriods. The settlement data of the first three secies. were statistically analysed and the average::, standard deviation and 95% confidence interval for the mean were worked out (Table II). Electra crustulanta PALLAS was found settling on anels during July, August, Setember, October, November and December. They were absent during the other arts of the year. The eak settlement 61

2 Unnilhisfuuan NCIir: OoserDations on tile fouling cliaract.!ristics of four 6r!JO?:oans in c:jcliin ftarl>our Table I HYDROCHLORICAL CONDlTIONS OF THE TEST SITE Month Surface water temerature C Min. Max. Av. Surface salinity %o Min. Max. Av. January February March Aril May June JUly August Setember October November December R I of this secies was in July followed by Setember and August. There was also a minor eak during November and settlement ceased by December. Thus settlement was confined to monsoon (May to August) and ost monson (Set. to Dec-.) eriods. The comaratively low salinity revailing during this eriod may be a condusive factor Jor thei settlement of this secies. During the occurrence of this secies the average salinity varied from 2.19% to 23.9% (Table 1). The eak settlement of this secies occurred at an average salinity of 3.13% in July. Electra crustulanta aears to be a tyical euryhaline form coloniing the estuary during the low saline conditions existing during the monsoon and ost monsoon months. Electra bengalensis STOLICZKA was noticed only during March, Aril, May and June with a eak in March at an average salinity of 3.27%. (Table II) i. e. during the first half of the re-monsoon eriod. The reduction in number during May and June may be due to reduction in salinity or due to aucity of larvae as suggested by Menon and Nair (197lb). 62 Electra bengalensis may b:! a tyical marine form colonising the estuary only during the high saline conditions of the re-mon so:m eriod. Schizoorella cochinensis Menon & Nair found settling during February to May (Premonsoon) and were totally absent during other eriods. Their maximum settlement was in May, when the 1 salinity varied from 24.5 to 32.4%. From the nature of occurrence this also aears to be a tyical marine form. Victorella avida KENT settled only during the monsoon and ost-monsoon eriods, namely, June, July, August, Setember, October, November and December. No settlement was noticed during other months. Peak settlement was in October. As observed by Menon and Nair (I967b) "the settlement of this secies in this locality indicates that the months most favourable for settlement are those when the salinity of the surrounding water is not high". The eriod June to Dec. forms the monsoon and ost-monsoon months and are eriods of comaratively low salinity. As also noted by Menon and Nair (loc. cit) high salinity of the medium is FISHERY TECHNOLOGY

3 <: t"' :><! z - ::"' Table II 5 ;:l Electra crustulenta PALLAS z :: Min. Max. Average Min- Max. "-l Standard 95% coufidence w Month No. of No. of Standard 95%confidence salinity Salinity Average deviation interval colonies colonies deviation interval %o %o %o %o "' o July (81-117) ;:! (2;19-4 8) August (28-46) ( ) ;:! 1:! :::: ;:1 <;l" '1 w Setember (34-49) ( ) - (\) October ( 8-18) ( ) November (23-53) ( ).: :::: December ( 5-9 ) ( ) <;;, Electra bengalensis stolizka. March (32-4) ( ). (\) Aril (2-3) ( ) May ( 4-7 ) ( ) June ( 1-13) ( ) Schizoorella cochinensis (Menon & Nair) <;l" February I ( 2-7 ) ( ).:: March ( 5-23) ( ) "' t:l ;::$ Aril ( -66) ( ) May (16-79) ;:: 2.17 ( ) ;,; 1:!!;:! '1

4 Unnilhisfinan Nair: GIJseroations en tl1e fouling cl1aracteristics of {our uryo:oans in cocfii1t ftar5ou Viet orella Pavida KENT Table Month Panel Rating Month Panel Rating Month Panel Rating No. No. No. --- June 1 R Set. R 6 c 2 R 2 c 7 c 3 R 3 vc 8 c 4 R 4 c 9 vc 5 R 5 c 1 vc July 1 vc Oct. 1 A 2 c 2 A 3 3 A 4 c 4 A 5 c 5 A 6 A 6 A 7 vc 7 A 8 c 8 A 9 c 9 A 1 R 1 A H c H c 12 R 12 R 13 c 13 vc 14 R 14 vc 15 R 15 R 16 R Nov, 1 R III 17 R 2 c 18 R '").J c 19 R 4 vc August 1 A 5 c. 2 vc 6 c 3 vc 7 c 4 A 8 R 5 vc 9 R 6 R 1 vc 7 c H 8 R Dec. l c 6 c 2 c 1 c 3 A 11 c 4 c 12 vc 5 R Key: R - Rare (below 5 colonies) c - Common (between 5 & 25) VC - Very common (between 25 & 3) A - Abdundant '(above 5)" 64 FISHERY TECHNOLOGY

5 Unnilhisfman Nair: Ooseruations on tlie fouling cfiaracteristics of four liryzoans in codiin liar6our unfavourable for the settlement growth and survival of this secies". Victorel!a avida aears to be brackish water form like Electra crustulenta and it can tolerate low salinities and even fresh water conditions. ACKNOWLEDGEMENTS The author is thankful to Dr. S. Z. Quazim, Director, CIFT for kindly ermitting to ublish the data. Thanks are due to Shri G. K. Kuriyan, Had of Division (Craft & Gear) for constant encouragement and to Shri R. Balasubrarnanyan, Section Head (CM) for critically going through the manuscrit and offering helful suggestions. The hel rendered by Shri H. Krishna Iyer in the statistical treatment of the data is gratefully acknowledged. REfERENCES Antony Raja, B. T J. Mar. Bioi. Assn. (India), I (2) Balasubramanyan, R and Menon, T. R J. Mar. Bioi. Assn. (India), 5 (2) Daniel, A 1954 J. Madras Univ., 26 (2), Garaathi, P. N., Lakshma:1a Rao, M.V and Nagabhushanam, R Andhra Univ. Mem. Oceanogr. 62 (11) , Iyengar, S, R., Goina'han, V and Kelkar, V. V J. De. Sci. Calcutta Univ. 7, Karande, A. A Proceedings of II International Congress on marine corrosion and joulii1g, Athens Kuriyan, G K. 195 J. Bombay Nat. Hist Soc., 49 (!) Kuriyan, G. K J. zoo!. Soc. India, 4 (2), L Menon, N. R. 1967a Ph. D Thesis, Univ:rsity of Kerala. Menon, N. R. and Nair, N. B. 1967b Int. Revue. ges: Hydrobiol. 52 (2), Menon, N. R. and Nair, N. B 1969 Proc. First all India Sym. Estuarine Biology. (In ress) Menon N. R. and Nair, N. B. 197a Bull, Natn. Inst. Sci. India (In Press) Menon N. R. and Nair, N. B. 197b Bull. Natn Inst. Sci India )In Press) Menon N. R. and Nair, N. B. 197c Curr. Sci Menon, N. R. and Nair, N. B Proc. Sym. Indian occean and adjuscent seas, their origin, Science and resources. Mar. Bio. Assn. India. (In Press) Menon, N. R. & Nair, N. B. 1971b Marine Bioi., 8 (4), Nair, N. Unnikrishnan 1967 Hydrobiologia, 3 (3-4), Nair, N. Unnikrishnan 1971 Fishery Techno!., 8 (2) VoL X No