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MARINE SPONGES OF THE INDIAN REGION 455 the Marine Biological Association of India 1980a. Demospongiae of Minicoy Island (Indian 16(1): 311-313. Ocean) Part-II order Poecilosclerida. Journal of 1975. Boring sponges of Zuari and Mandovi the Marine Biological Association of India esturies. Bulletin ofthe Department of Marine 22(1&2): 1-7. Science, University ofCochin 7(1): 1 17-126. 1980b. Demospongiae of Minicoy Island (Indian 197P6oae.ciElnodseclcetryiodna,laRmaeslplaoislaiind.aesp).(fDroemmosthpeonIgnidaiea:n HOacderaonm)eriPdarat,-IElpli.poOlrasdiedra aHnadliCchohroinsdtridiad.aJoaunrd- seas and a revised key to the Indian species of naloftheMarineBiological AssociationofIndia Endectyon Topsent. Journal ofthe Marine Bio- 22(l&2):8-20. logical Association ofIndia 18(1): 169-172. 1983. Distributionandaffinitiesofthespongefauna ofthe Indian region. Journal ofthe Marine Bio- 1976b.Historyofspongiologyofthe IndianOcean. logical Association ofIndia25(1&2): 7-16. Journal ofthe Marine Biological Association of 1984. Sponges collected aboard R.V. 'Skipjack' India 18(3): 610-625. from thesoutheastcoastofIndia. Journal ofthe 1977. Studieson Indian spongesVIII, Fournew re- MarineBiologicalAssociationofIndia26(1&2): cordsofsiliceousspongesEchinochalinaglabra 95-102. (Ridley& Dendy),Higginsiamixta(Hentschel). 1985. Demosponaiae of the Gulf of Mannar and Geodia lindgreni (Lendenfeld) and Pacham- Palk Bay. Pp 205-365. In James, P.S.B.R. (ed.) philla dendyi Hentschel from the Indian Ocean. Recent Advance in Marine Biology (Today To- Journal ofthe Marine Biological Association of morrow's Printers and Publishers: New Delhi). India 19(1): 115. THOMAS, P.A., RAMADOSS, K. & VINCENT. S.G. 1979a. Boringspongesdestructivetoeconomically 1993. Invasion of Cliona margaritifera Dendy important molluscan beds and coral reefs in the and C. lobata Hancock on the molluscan beds Indianseas.IndianJournalofFisheries26(I&2): alongtheIndiancoast.JournaloftheMarineBio- 163-200. logical AssociationofIndia 35(1&2): 145-156. 1979b. Demospongiae ofMinicoy Island (Indian THOMAS. PA. & THANAPATI, V. 1980. An ancient Ocean) Parl-I, orders Keratosida and Haplo- windowpaneoysterbed inGoawithcomparative sclerida. Journal of the Marine Biological notesontheOysterin an extentbed. IndianJour- AssociationofIndia21(1&2): 10-16. nal ofFisheries27(1&2): 54-60. THE IMPACT OF TRAWLING ON SOME duetotrawling,foratleastoneormoreofthemeasured TROPICAL SPONGES AND OTHER SESSILE attributes. For all benthos taxa combined, the rate of FAUNA. Memoirs ofthe Queensland Museum 44: decrease in benthos density with trawl intensity 455. 1999:- Following a replicated repeated-trawl corresponded to -10% per trawl, so that in areas depletion experiment, which removed 70-90% ofthe trawled 13times,thebenthosdensitywasonly-25%of initial biomass of sessile fauna, non-destructive that in un-trawled areas. This conclusion was very methods have been used to measure recovery ofthe similartotheoverallestimateofremovalobtainedfrom structurally dominant species. To date, three depletion-regression analysis of the catch obtained post-impactsurveys have been completed (1 month, 1 during the repeat-trawl experiment. The results also year, 2 years) on 6 trawled swathes and 6 controls. indicated the nature in which trawl impact was These involvedquantitativevideoobservationsfroma manifested for different organisms with different tow-sled and from an ROV withpositioning precision structure and morphology. The sea whips were most of2m.Morethan80taxaofsessilefaunawererecorded resilient to removal, though they could be damaged. andabout 15 taxa, includingsponges, gorgonians, and Spongesandsoftcoralswererelativelyeasilyremoved alcyonarians and hard corals, were abundant enough and hard corals were easily broken. The gorgonians foranalysis.Theattributesmeasuredforeachorganism were intermediate and variable in resilience. The were species, position, size (height, width, and area), interaction betweenthesedifferencesandtrawl impact and condition (proportion intact, dead, or encrusted). caused a marked change in, and degradation of, the Thesedataenabledanalysesofdensity,size,condition community composition of the seabed habitat. O andspeciescomposition,withhighprecision. Wehave Porifera,sessilefauna, impact, condition,recovery, trawling, demonstrated statistically that the methods are very ROV, video, resilience. powerful fordetectingrecovery on thetrawled tracks, bruetcotvheeryt.imNeevseerritehselise,ssa,s yient,ttroeoatsmheonrtttvosidceonnttirfoylanoyr CC..YR.. BPuirtrcihdegre,(eTm.aJi.l:Warsosleanndb.eprigtc&herG(.dP\.maSrmmiet.hc,simC.Sa1uR)O, beforevsaftercomparisons,alltaxaanalysedforwhich DivisionofMarineResearch, POBox 120, Cleveland, Qld. sample size was adequate, showed significant impact 4163. Australia: 1June 1998.