During the summer of 1948 the writer was employed at the Virginia Fisheries Laboratory: for the purpose of assisting with routine work in connection with the oyster population studies as well as to devote some time to investigation of the practicability of utilizing chemical repellents in control of the oyster drills (Urosalpinx and Eupleura) . Initial work was carried on to determine tolerance of the young oyster spat to various chemicals, and usually the optimum conditions were determined before introduction of drills

Hoffman, Richard L.

English

College of William & Mary: W&M Publish

W&M ScholarWorks Reports 1948 Report on chemical control of oyster drills, 1948 : summary of experiments Richard L. Hoffman Virginia Fisheries Laboratory Follow this and additional works at: https://scholarworks.wm.edu/reports  Part of the Marine Biology Commons Recommended Citation Hoffman, R. L. (1948) Report on chemical control of oyster drills, 1948 : summary of experiments. Manuscript. Virginia Institute of Marine Science, William & Mary. https://scholarworks.wm.edu/reports/2663 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. t > REPORT ON cHEJ:.IcAL CONTROL OF OYSTER DRILLS, 1948 Sunne...7 of E:;...--pr·r:i.ments _Richard L. ~ffman During the summer of 1948 the writer was ,employed at the Virginia Fisheries Laboratory: for the purpo_se of assisting ,,ith routine ~-rork in connection ili th oyster population studies as well as to devote some time to investigation of the practicability of utilizing chemical repellents in control of the oyster drills (Urosalpinx and Eupleura) . Initial ,rork was carried on to determine tolerance of the young o: ster spat to various c:1emicals, and usually the optimum conditions ..:ere detern:ined before introduction of drills. Considerable difficult:}r was encountered in securing sufficient qus.ntities of mat erials from one time to the next, as well as mainuin-ing an:i.muls alive in the laboratory tanks. The latter was complicated by fouling through deposition of sediments in the river, ~md affected wire cages suspended in the open water as well as indoor tanks . In addition to quantitative e:;:periments, same observations ·.-,ere made from time to time on the behavior of the o:·ster drills that were kept alive . These notes are appended as they "I!'.ay be of some interest : EXPERIMENTS iHTH CHj<;?-fICALS Couper sulphat e : This metal salt w~s first.used be.c~use of its alledged success at othGr localities. Unfortun~tely, e. h .... ndicap 1-10.s imposed by the lack of exact information regarding conc~ntration of solution and mode of a.,:rli-cation. Considerable time and effort was sp·ent investigating these fac-tors, and no really satisfactor-J conclusions were reached. {)(Q) tt,S \J\T'I~ L 4-&:i "J. .q \-l(o l( \ q ·\~ On July 2, oyster shells including nearly 150 young spat (greatest s i ze range up to about 40 mm) wer e treated by immersion in 5 different concentra-tions of copper sulphate, as indicated in the following table. In all three cases the solvent was 1 liter of fresh water, ·to which 10 ml acetic acid was added. This resulted i n a solution 0f nearly the sem.e aci dity as ordinary vinegar. Five minutes was the time of immersion in all cases. The three batches were placed in wire baskets suspended in an aquarium. After several hours macy were slightly open, and seemed to be none the wor se for their experience (closing readily when touched) . On July 5, the following obser-vations wer e made : Maey s1>at dying, the shells saping and the meat easily seen. 'Ibis is true of spat di~ped in al,1 three concentrations. The spat in the control aquarium t:lo not show any injury or mortality. Lot No. 198 199 200 TABLE I CuS04, gms. per L. No. Spat 1 5 25 46 50 47 No . Dead on July 10 45 42 34 The mortality rate as indicated above is.not reflective of concentration, the death rate does not correspond to the higher a.mounts of copper s-..ilphate. However, the next experiment was directed along the lines of very l ow concen-trations, and furthermore the spc3:t were wush~d in fresh water f ollowing immer-sion. On July 12, a,::ipraximately_ 56 spat were·used in a way as f ollows: 12 were dipped, for 5 minutes, in the solution of 10 ml. ~cetic ~cid in one liter of water, with the copper concentrations 1, 1/10, and 1/100 gms . per liter. TABLE II Lot. No. Solution No. Spat Used No. dead JuJy 17 198 1 gm . CuS04 15 9 199 1/10 gm. CuS04 12 7 200 1/100 gm. CuS04 12 6 2 The resultant mortalicy of nearly ·so;;: reg!::.!'dless of concentration, cast ~ reflection on the advisibili-cy of continuing use of aquarium ""or e:h'Pe:-:ilnenta.l material. n:his was ampli:'ied by the fact that a.bout a damn spat, di}Jpetl at the same time in a solution of 1/10 gm. CuS04 per liter for -f'ive minutes but laced in e shallow enamel pan 11ith running water suffered a mortali-cy of but qbout 10%. A second experiment ~.f the same nature was commenced, ·rith the se.me conditions efter a week , and yieHied about the same results. Therefore, it was decidec.1 to place treated spat in wire baskets·· ano. suspen~ these in the river. On JuJy 15, six lots of spat were treated under the condiitions indicated below (numbers ref er to compc..rtments in the lrire cage used): 26. Control. Undipped spat , 18 in number. ?5. ?l :;:pat dipped in dilute acid solution (1s·m1 per L.) for 5 minutes. 24. 21 spat dipped in 1 gm. CuS04 per liter, for 5 minutes. ?5. 25 II II 1; l6. II II II 1 minute. ')?. PS ,, ll II ::./10 II II II 5 minutes. i?l. 18 II II II 1/100 I' II II II ,. .  On JuJy 19, e:an:ination of these lots: following 4 da;;,-s in the river, shows that 11most if not all of the spat are still alive. 11 Accordingly, since the initial high mortali-cy seems to ha.ve been caused by laboratory envoirnment rather than chemicals, it was decided to increase copper concentrations and commence ex~erimental use of drills. The table in-dicates conditions and results. Time of immersion was five minutes in all cases. TABLE III Lot No. [ilo:r;i.c. of CuS04 in gms. per L. No. Spat No. Dead on Ju:cy- ~8 181 1 "l 5 18:? 5 ?5 2 185 10 20 1 184 15 f..O 4 185 ?O ?O 7 186 Control, no copper 21 1 3 ' At these.me time (July 19) about 21 spat were dipped in a solution of 1 gm. per Liter for five minutes and placed in a separate wi~e basket -,d.th 25 specimens of Urosalpinx of all sizes. On JuJy 28 it was discovered that the solution did not repel the drills. "The wire baskets containing the r1 spat ••• was examined. 15 were drilled, all sizes up to 50 mm. Drills all seem well and hapw. Some have laid ·eggs. Most drilling at time of obser-vation.11 The results of the experiment surmnarized in Table III indicated that solutions of more than 10 gms. per liter were undue]y toxic to the spat. At the same time, the concentration of 1 gm. per liter did not in arw sense serve t o repel the attacks of drills •. Therefore the amount was raised in an n.ttempt to determine if a greater concentration would be efficient. The following experiment was made on Ju]y ?9 and checked a week later: ' TJJ3LE IV -,ot No. Cone. in gms. per L. Time Dipped No . Spat No . Dead 198 10 10 min 57 9 199 10 15 , in 28 10 25 drills were used in each instance. On August ?4., additional work was done uith corper sulphate us well as . .. with other chemicals, the latter:discussed under their respective places. 17 spat were dipped for one minute in a solution of 100 gm. CuS04 per liter slightzy acidified "ith 5ml acetic acid. These, .;ere placed in a basket with 10 drills. On A..igust 50 , seven of the spat v:ere dead and 10 -,rere alive, and none were drilled. 4 A final trial 1,as made on September 5, using solutions without acidification . Time of i.nnnersion was one minute. On September 8 a check was made on mortality und several drills were introduce.d . into each compertment, a.nd further checks were made on September 16 e.nd 27 . 5 . TABLE V :.Ot 'lo. Cone. o:tl CuS04 Ho.Spat No.Dead No. Dead no. Dea6. in gms./1. Sept. 8 SeQt. 16 SEut. 27 Box- Drll. Box- Drll.-Total 45 l 25 1 box 1 0 1 0 44 5 22 none 2 0 2 0 45 10 ?.4 4 bexes 4 0 8 5 46 25 27 12 boxes 17 0 18 5 47 100 25 5 boxes 15 0 20 1 Frc:8'.!l the above it will be seen that the higher concentrations caused a very high mortali-w, up to 90% in lot No . 47, and usually resulted in a high ini tie.l mortality. It is notewortey that concentrated solutions did not in-terfere with drill activiti es. It would seem that the results of "i.m:Qlersion in low concentrations, up to 2 4 15 21 21 5 gms. per liter, gave the best results • This information compares ve-r'J favor-ably with that found in Table III, for Lot. No . 182 . Mercuric Chloride: Two experiment s were run involving this chemical, in which immersion of the spat in a very dilute solution was the mode of application. On August 24 , the f'ollowi ng solution of HgCl was made up , amounting to about one liter: l pt . caturated HgC:l. sol ution, 10 pts . water, 1 pt. satu-rated (Be 40) sodi um silicate solution . S;at were dipped for about a minute, and placed in a wire cage with 20 drills. After an interval of one week it was found that 12 spat were dead, 15 alive, and none drilled. In all cases t he drills wer e rarely on, or even near, the spat . On September 5, another eJ..l)erimrnt was initiated involving use of HgCl and run simultaneously with one using copper sulphate (cf. Table V supra) . 6 .. T.A.BLE VI Lot . Ho. Cone. of HgCl .:..n No . Spe.t No . Dead Ho . Dead Ho . Dead gms. / liter Sept . 8 Se12t . 16 Sc:et . 27 .-Total Box.-Drill Box.-Drill 58 1 ?.5 5 2 0 5 0 5 59 5 25 9 7 0 17 1 18 40 10 20 8 6 0 6 0 20 . Here again lower concentrations seems to be more satisfactory, although the lowest mortalizy of 20% is rather high for practi cal purposes. In this chemical there seems to be a correlation between death rate and concentration. In conclusion, it msv be said that the use of a solution of 5 gms. of copper sulphate in water , without acetic acid, appears from the available data to be the most profitable conditi on to recheck, if that is deemed necessary. It may be that the acid has an effect causing the spat to relax their adductor muscles and permit entry of the copper sulphate. NOTES ON BEHAVIOR OF OYSTER DRILLS A more or less casual, quail ta.tive series of ob::;ervations were made on the behavior of oyster drills maintained alive under varying conditions. .b.11 notes (main]y by J. D. Andrews) are herewith a.,;pend.ed inasmuch as they may have some slight bearing on the wide aspects of the drill control problem. Ju]y 20 . 111-:lassmann brought· in some jingles from ~-!ormley 1s Rock this morning. A few of the cleanest shells bearing jingles were selected and the remaining macroscopic organisms cleaned off . These shells did not have a:rzy- oring sponge. Jingles were sel ected and numbered from 1 to I3. Jingles 1-4. had the upper valves r~hened with the point of a knife under a binocular mieroscopc._ Jingles 5-9 were not treated in arv manner. These two batches of jingles were put in a wire basket suspended in a. large aquarium and a dozen drills edded. Jingles 10-15 were not t r eated but were placed in another wire basket in the same aquarium for controls. A vigorous aerator has been installed in t..he aquarium to replenish thew-gen and cause some movement of the water." ~ 21. 11At first a couple of drills hover ed at the entrance to j.ingle shells for an hour or two. All this t ime t he j ingles next to the drills wer e openi ng and shutting their top valves with apparent]y no fear from the pre-7 sence of drills . Today the drills have not even stayed near or on the jingles and no indications of acy- boring are. seen. All the jingles are alive and feeding. Thi s whol e observation suggest s that ther e i s something refr active about the j i ngl es other than di ffi cul-cy in bor ing t he shell. For I see no evidence that aey drill has tried to bor e through the shell. Tonight I put an cy-ster shell with 5 spat (4 on top and 1 on the lower shell) in the aquarium to see if thG'/ vill drill oysters. Another shell with 5 spat was put in the control basket. All barnacles, dead ancl a.live were cleaned off so nothing macroscopic remains for them to eat . JDA. 11 ~ ?4 . "Four of the five cy-:=ter spat placed in the aquarium on 21 J~r have been drilled and the meat is gone. 'lhe remaining spat has been drilled some but interrupti ons caused by too frequent examination have saved it is far . All of the jingles art? het:.lthy and living. There is no indication Of drilling • II ~ 26. "After their excellent feed last week end (all spat put in ?6 J~r e.re dead) a.boat half of the drills have "ound it possible to l~· a batch of eggs - several groups of 5 or 6 egg cases are visible now l•here tnere were none Saturdey (24th) . n " 8 .August 16. "Two large flat'pans were set up with the idea of trying to determine what drills do in the presence of v~rious foods as well as jingles. In pan 1, about 50 x 40 cm. with 1 cm of water, ten drills were placed in the center with 1oring sponge in one corner, mussels in another, spat in & third, barnacl es in the fourth: and ·jingles along one side unc'er the water supp]y. The drills began to move'almost at once and dispersed to one side of the pan where they by-pa sed 'the barnacles and made for the water supp]y. By the next day a.11 had accUJllulated there, and in about a week began to fil-ter towurds the organisms, showing no special preferences. Jingles 11ere ig-nored. In pan 2, same size as above, and with same water conditions, 10 drills were placed in the center and a number of jingles i:,laced directly 1.mder the water supply. t-!ithin a day the drills had either gathered under the running water or gone over the side of the pan • .After a week no signs of drilling were noted despite the fact the jingles were serving as a substratUJll. 11 Similar observations made at frequent intervals during the summer all point to the fact that some intrinsic factor other than possible in-vulnerability of the jingle shell. is responsible for the indifference of drills to Anomia. On severnl occasions hungry rdrills were off erred shucked jingle meat but never showed interest in it before it h&Q time to become bad. 

Report on chemical control of oyster drills, 1948 : summary of experiments

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Report on chemical control of oyster drills, 1948 : summary of experiments

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