Mann, Roger L.

English

College of William & Mary: W&M Publish

W&M ScholarWorks Reports 1-12-1989 Field Studies of Comparative Settlement of Oyster Larvae on Oyster Shell, Expanded Shale and Tire Chips Roger L. Mann Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/reports  Part of the Aquaculture and Fisheries Commons Recommended Citation Mann, R. L. (1989) Field Studies of Comparative Settlement of Oyster Larvae on Oyster Shell, Expanded Shale and Tire Chips. Marine Resource Report No. 89-2. Virginia Institute of Marine Science, College of William and Mary. http://dx.doi.org/doi:10.21220/m2-k771-vf90 This Report is brought to you for free and open access by W&M ScholarWorks. It has been accepted for inclusion in Reports by an authorized administrator of W&M ScholarWorks. For more information, please contact scholarworks@wm.edu. VIRGINIA INSTITUTE OF MARINE SCIENCE, SCHOOL OF MARINE SCIENCE, COLLEGE OF WILLIAM AND MARY MARINE RESOURCE MANAGEMENT REPORT 89··2 Field Studies of Comparative Settlement of Oyster Larvae on Oyster Shell, Expanded Shale and Tire Chips by Roger Mann Virginia Institute of Marine Science Period of Field Studies: Site of Field Studies: Date of Report:~ Introdu.c t i_on August 5, 1988, through September 16, 1988. James River, VA January 12, 1989 Following the presentation of the report prepared by Dr. R. J. Byrne to the July meeting of the Virginia Marine Resources Co@nission, a request was made to the Virginia Institute of Marine Science (VIMS) to evaluate expanded shale (Solite) and tire chips as alternative cultch to oyster shell. This evaluation has three components: laboratory (flume) testing of mobility, laboratory studies of settlement using cultured oyster larvae, and field studies of settlement. This document describes the protocol and results for the field study component of the evaluation. Pn:itocol_ \ Present monitoring activity utilizes oyster shells threaded on metal wire. The expanded shale substrate is not suitable for drilling and threading; therefore, the materials were exposed in plastic mesh, one tenth bushel volume "tubes.". Rather than attempt to quantify settlE·ment as oysters per unit area, we compar~d settlement per unit packed volume of substi-ate. In mas.s "planting" of substrate this ~·muld, effectively/.-)Je the comparative yardstick anyway, so the approach is meaningful. The tubes were 18" in ci1·cumfer-ence and hi:1d a mesh sizE) of 1". "Tubes." r~ere deployed in t.:he James. l=<iver, \)ir·ginia, on the fol J.m,,ir,g dates: August 5, August 19 and September 2, 1988. This coincides nith the period of generally high oyster settlement in the James. The sites of deployment were Naseway Shoal, Rock Wharf, Wreck Shoal and Point of Shoals. ,-These sites were chosen to provide good spatial coverage to cover possible variability in intensity of settlement. (.H: ea.ch of the Lt stations si:-: "tubes" 1,H=.,1--e dPployed, hm contain:1 nq each of shell, expanded shale and tire chips, in early August. At three of the stations the "tubes" were hunq from ne1A.1ly placed stakes.. M.: the fou.d.:h station (Naseway) we used an old pound net pole. Stakes were placed and "tube:=:." deployed on August 5, 1988. T.K• week=· later· the "tubE!s" ,·1ere retrieved and replaced with further, previously unexposed tubes. A third deployment i.~nd retr·ieval fol lm,1ed the second as continued sE-ttlement: Vici=· ob5.e1-ved in the Jame!::. on t:he adjacent 11 shell!::.1Ting" monit:or·inq =·t:ati.on. Retrieved mate,·ial was dried and subsequently examined microscopically for presence of settled and metamorphosed oyster larvae. A two-week deployment: C ..ia.s chos.en rathei- than a one-i,,teek deployment in 01--der to: (l) ma,:imize ::,ettlement pE:r unit c:ultch while stUl r'f:?.maining sufficiently short to minimize growth of fouling organisms; (2) to allow sufficient time for spat to grow to facilitate observation; and (3) eliminctte~ the nF2ed to maintain the 11 tube 1' aft:e,- 1-f:;t.:r·ieval for a 11 qn:<~·1 out" pei-iod whE•n !:.pat mortality or accidental fui-ther settlement (through the sea water supply) may occur. < ' . C Results Data are expressed as oyster spat per unit (0.1 bushel) volume of packed cultch for each station and deployment period in the accompanying table. The numbers a,-e then expressed as a percentage of the total spat count for all substrates at that site for that collection date. To allow statistical comparison of settlement between the substrates within a single site and date the percentage values were arcsin transformed. Comparisons were then made using ar1alysis of variance (ANOVAl. Overall the shell was, by far, the preferred substrate. In 11 of 12 replicate comparisons shell had the highest proportion of settled spat. For the entire experiment setting on shell was significantly greater than on other substrates. The ranking of the substrates varied statistically with time even though the general trend was consistent as shell)tire)shale. For the first time period (8/5-8/19) setting on shell was significantly higher than both shale and tires. For the second time period (8/19-9/2) setting on shell was significantly greater than shale but not statistically greater than tire. For the third time period (9/2-9/16) significant differences were observed for all substrates (shell)tire)shale). Although differences were observed between stations this was considered due to spai\al variation in settlemement throughout the river, something that is well documented. The relevent comparisons are at a single station within a single time period between different substrates. In summary, shell is a better substrate than tire chips, both are better substrates than shale. i I I i I ! [ - ~-C Compai·ative Settlt?ment of Uy!::.ter Spat on Three S11b!::.trates in the James River, Virginia during August - Septe~Jer, 1988. All spat numbers are per 0.1 bushel. Percentages are of total for all substrates at that locatio~ for that period. station e;.:po!::.\Wt? pt.?r· iod !::-hale su.bst.:i-ate tin, s.he 11 spat y-;_ c:ir·csin 8./5--8./ 19 Nase.~ay Eihoal 87 20 .1 2t1 .6 Wreck Shc,c:d 138 18.7 25.6 1:::ock ~Jharf 92 11.6 19.9 Point: of Shoal 4-6 2lt .6 29.7 8/ 19--9 ;;_:.~ Naset<\lay Shoal ~)'7 c., 27.6 31..7 Wreck Shoal 21 26.9 3l.2 F<nc:k lslharf 12 9.4 l7.B Point of ShoaJ. 14· 16.3 23.8 9./2-9/16 Nc.,se,Jay Shoal 8 L ~, 7.5 ! kir-E)Ck Shoal ~5 7n9 16 .. 3 Pock Whc1rf .12 Cl ~1 9n5 l... .. t1., Point of ShoaJ. Cl )... 2n6 9.3 s-pat % ar·csin 77 17.8 i?. 1-t. 9 194 26.3 30.8 187 2::--:l.b 29 .1 32 17.1 2l+ .4-23 23 .. 5 29,.0 3'+ 43.6 4L3 4.1'.t 34 .. tJ 36.,(i 2i? 25.6 30 .I+ '"' 1-ft.! 9.4 1 '") C" ! • d u 7 n ~s 24 .. 7 47 l.0., L+ 18.8 1 ·.:i ).._ 1 ~-=-i. 4. 23. 1 sp,c1t 269 l+(l6 ~314 109 48 23 71 ~50 L~26 ,~.7 39'.:\ 6'+ •1 ·'' 62 .1 55n(l 64.8 58.3 48.9 29 .!:'i 55 .. 9 58. l 88.9 '7'+ .6 B6. ·-:; 82.0 ANOVA Results; nsd denotes no statistically significant difference (11 1 way comparing substrates, all dates: F = 45.1, P < 0 .. 00001 shell > tire, tire and shale are nsd. (2) 1 way comparing substrates, 8/5 - 8/19: F = 72.,67, P < 0.00001 shell> tire, t:ire and shale are nsd. (3) 1 way comparing substrates, 8/19 - 9/2: F = 7.03, P < 0.001 ar·csin 52.0 47.9 53.6 49.8 4l1 .4-32 .. 9 48.4 49 .. 7 70 .. ~ 59.7 68.8 bl+ n 9 shell and tire are nsd, tire and shale are nsd, but shell ~ shale. (4) 1 way con~aring substrates, 9/2 - 9/16: F = 211.,4, P < 0.00001 shell } tire} shale. 15) 1 way comparing dates, shell only: F = 12.2, P < 0 .. 003 period 1 and period 2 are nsd, but both are< period 3 (6) 1 way comparing dates, tire only: F = 9.72, P < 0.0056 period land period 3 are nsd, but both are< period 2 

Field Studies of Comparative Settlement of Oyster Larvae on Oyster Shell, Expanded Shale and Tire Chips

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Field Studies of Comparative Settlement of Oyster Larvae on Oyster Shell, Expanded Shale and Tire Chips

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