Fishe r i e s and Marine Se rv ice

Technical Report No. 797

OYSYER LARVAL POPULATIONS AND ASSESSMENT OF SPATFALL

RLDFFORD RIVER, P. E . I . , 1963 and 1964.

i I r h c r ~ c s ,inti i rkv lronmeni &I Sc I erlce., Fisheries and Oceans Canada, Ha l i f ax Laboratory, P. 0. Box 550, Ha l i f ax , Nova S c o t i a B3J 2S7

'L'lris work was tiot~e undcl- tlic 1:ishcries ilesenrch I3oard a t i t s Hiologicnl Suhs ta t ion a t i l l l c r s l i e , Priitcc EJw;rrtl I s i and .

Report Prepared tinder Corrtract t o Resotrrcr Rrai~ch, l'i 5he r i e s and M a r ~ n e Se rv lce , Marl tlnte Regi or]

'hr. B . S ta l lwort l iy , Ruggles Gates 1)rofessor of Biology, Mount Al l i son l in lve r s i ty , S a c k v i l l e , New Rrunswick, Canada. Present addres s , - - Apt. 1007, 8315 - 105 S t r e e t , Fdmonton, A lbe r t a , Canada. T6E 4H4.

Lhii-in!: t h e slimiers o f 1958 through 196.1 an in tc i i sc 1,royrcinime was c a r r i e d ou t monitoring loca t ion and delis-

t i e . o f yopula-tions of t h e l a rvae of Crassostreri v i r g i n i c a (Cmelin), a s w e l l a s t h e i n t e n s i t y o f t h e

s p a t f a i l , I t s o r i g i n a l purpose cen t r ed around t h e need f o r more e f f i c i e n t commercial u t i l i z a t i o n of s p a t f a l l .

S ince curnmercra~ c - o l l e c t n ~ s were not always ca t ch lng s u f f ~ c i e n t s p a t t o pay f o r t h e l r c o n s t r ~ t c t r o n , t h e f i r s t

s t e l l 1.1 rn7pro\irrg t h e ca t ch scerned to be a more accura t e k-iowledge of the d i s t r ib i i t 2on o f t h e l a rvae rn t h e

wa te r . 'This could tlieri bc rr?;i teii t o spat c o l l e c t o r r e s i r i t s . With einllliasis on predicr io i i tile Collowic~g aims

devc ioj)cd.

a ) 'Io Inprove t i le ,iccur,icy of p r e d l ~ t r o n of s p a t f a l l both i n t lmr (da te ) and In ipace {horizont,rl a11d

v e r t l ~ a l )

b) m e q u a n t l t a t l v e p r e d r c t i o n o f s p a t f a l l s . Once q u a n t r t a t i v e lnformat lon on .arval populations 1s

a l , a i l ab le , correlations may be a t tempted with t h e corresponding s p a t f a l l s .

c ) Long-term s p a t f a l l p r e d i c t i o n . Long-term t r e n d s i n weather and hydrographic c o n d l t l o i ~ s mrght a l s o be

usoful ns p i e d l c t i o n f a c t o r 5 once ' i tcura te t iescr lp t lon of tire l a r v a l popui ' i t lon i s a v d l l a h l e Other c o r r e l a -

t ! o i l \ wi th ~ d i I O U \ feIiI (11 ~4 of the cilv I 1 rliriiirrit I rat11 l y ".i~fificit tilemsulvei Ainoilfi t i ~ c % c , I,iirn,iri in ter f: I crice,

tllr. i : r o w t ii i l l ol1:r.t tri&,ilr!slliz w i i i ~ 15 , i d 1 1 1 I : I \ & I t * ! \ &,I c v c i i t tt3c*s i i i 1 ~ ! 1 1 I i c . tor:\it!i*ri~ii 1 1 1 t , A I , I ( ( i i t . : t < *

qiidrrt lr,it ~ v c cieii I i p t ion oi t h e lar v,tI j ) ~ p i i i < ~ t 10i1 J s c i l e n t id1 t o t l ic i v r rnu la t~on and siibsequerrt I I i v c ~ ~ i i gat IOII

o f almobt any f a c e t o f t h e l l f e o f t h e o y i t e r l a r v a and ~ t s s e t t l e m e n t .

Some thought was a l s o given t o t h e p o s s i b i l i t y t h a t s imple r methods o f p r e d i c t i o n o r o f s p a t c o l l e c t i o n

might be fourid and t h i s a spec t o f t h e programme was s t a r t e d i n 1958 i n t h e t e s t i n g o f o y s t e r coi id i t ion f a c t o r s

a s an i n d i c a t o r of spawning. Simple c o l l e c t i o n niethods were l a t e r taken up by .I . i:. ?Iedcof i i i tile

t e s t i n g o f var ious types of c t ~ l t c i ~ wliicli has bceri r epor t ed a l r eady (1351).

A \ trme wont on t h e rnagnrtudc and ~on i l ) l t x l ty of t h e mere description of t h e iarv,i l p o p u l a t ~ o ' i ~ l ~ i i ~ i i c d our

t o t a l ~ ~ t i r e n t l o i i , iii~ii e f fc i t s t o ice'n iiiiiplcr p r e d l t t loll or co i l e c t :on nrctlrodi were dropped from the rrogr'lmrne

i t bec,i:iie neceisarq t o 1 0 0 ~ ~t t h e > r e t i c , i l inoilels ti) he lp t o i n t e r p r e t d a t a from tile tompiex l a rva l piipulation

:nrthernlori: t h e i n v e i t i g a t i o n of t h e c luan t l t a t lve n s p e c t i began t o suggest Important ques t ions about t h e b i -

ology o f the o v s t c r l a r v a e , t h e r r p r e d a t o r s , food slipply and e s p e c ~ a i l y t h e i r behavlor

TABLE OF CONTENTS

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.&bseract/Kesume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

hfethods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pump Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Spat collectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fractional Counts of Spat on Scallop Shells - - - - - - - - - - - - - - -

i{esults and niscllssion --------------------dm--------------------

Larvae and Spatfall, 1963 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Larvae and Spatfall, 1964 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Gon~parison of 1963 and 1964 Larval Populations - - - - - - - - - - - - - - -

Spatfall in Smelt Greek vs Paugh's Greek - - - - - - - - - - - - - - - - - -

Vertical Distribution of Spat . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Accuracy of spat counts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mortality --------.----------------------------------------

4sbestos Board as ('~itch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Biniontiily Si~ells ;is Spat Collectors . . . . . . . . . . . . . . . . . . . . . . . . . .

\$eatiier and Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.&pppeiidix T i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appeiidix 111 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

,&ppendix I\i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ii

iii

i v

1

2

2

2

2

2

5

6

7

7

8

8

8

iii

ABSTRACT

Drinnan, R . E. , W . 3. Stal Iworthy, 1978. Oyster larval populations and assessment of s p a t f a l l , Bideford

River, P , E . I . , 1953 and 1964, Fish, Mar. Serv. iechn. Rept, No. 797 pp.

In t h i s , the l a s t i n a s e r i e s of annuai s tud ies of oyster larval dynamics and s o a t f a l l in t h i s a rea , no

s i g n i f i c a n t c h a ~ g c s i n techniques were Introduced.

As compared do 1963 the spawning In 1964 was l a t e ard s l l y h t , larval concentrations were muck lower, spa t -

f a l l l a t e and much l e s s (1963 ~ e a k 26-28/7, 1964 peak 3117-3/81. Day-larvae (Mature)/iOO l i t r -es were i n 7963,

3730 and i n 1966 only 96% Larval mortal i ty was orea te r (up t o 20%/day)in 1964. The s e t t l n y index varied From

63.6 to 17.8 wh~ch lndlcated a lack of cor re la t ion betwen the concentration o f mature larvae i n the water

and the -intensJty of s e t t i n g .

Two major t r ib t i t a r les of the es tuary , Paughk Creek and Smelt Creek were compared i n both y e a r s , i n the

good year (3963) Paugh's Creek was exce l len t while Smelt Creek was good. In the poor year (1954) both creeks

were f a i r but Smelt Creek was b e t t e r than Paugh" Creek. Spa t fa l l peaks were synchrunous i n the two creeks i n

bozh years , This may be re la ted t o weather and t i d e s . Length o f larval 71Fe was c lea r ly 22 days i.i 1963, b u t

i n 7 964 1 t appeared t o be only 75 days w h i c h may hade been caused by the recrkti trnent of o lder larvae whose

antecedents had not been observed.

Cai?ec"Lors w i t h s h e l l s chanqed bifionthfy {were found s a t i s f a c t o r y f o r rout ine ir-rorlitoring of s p a t f a l i s , but

not f o r accurate observation o r s e t t i n g peaks. Asbestos board was found i n f e r i o r , although adequate, as a

c o l l e c t o r of spa t a s conlpared t o sca l lop s h e l l s .

Key words: Oysters; Crassostrea v i r g i n i c a , larvae, vel i g e r s , s p a t f a l l , populations, mortal i ty .

~fisurf Dans c e t t e dernlPre d'une s e r i e d 'btuaes annuelles de l a dynamique des larves d%huitre e t de l a tombhe

du na i ssa ln , aucun cnangewnt s l g n i f l c a t i f n ' a 4t6 apporti. Zi la mgthooe.

Comparat~vement au f r a ~ de 1963, ceiui de 1964 a 6t6 t a r d i f e t peu Important, i e s cancentratlons de

ia rves e t a l e n t de beauco~p 1nFi5rieures, ? a tomb& tardlve e t beaucoup moins importante jmax~nrum dr 1963: du

26 au 2917; rnanirnum de 1964: du 3117 au 319). i e nombre de journ6es-larves matures pour I00 1 6ta1 t de 3,

730 en 1963 e t du seulement 969, ea 1964, La anortalit6 r: 6t6 plus importante i n 1964 (jusqu" 220 % par jour)

LYndice de f ixa t ion var ia i t de 63,6 a 77-8, ce qui indique u n manque de c o r r 6 l a t i o ~ e n t r e l a concentration

des i a rves natures dans I 'eau e t 1 ' i n t e n s i t 6 de la Fixation.

Deux t r r b u t a t r e s importants de I ' e s t u a i r e , l a ruisseau de Paugh ei; l e ruisseau Sm1 t ont &ti? cornparks

pendant l e s deux annkes. Pendant l a bonne annge (19631, l e ruisseau de Paugh a 6t6 exce l len t t and is que l e

S s e l t 6tar t bon. Pendant l a n;auvaise annee (1964), l e s &ux ruisseaux & t a l e n t passables , mais I& Smelt

& a l t m e i l l ~ u r gue 1 ' a u t r e . Les maxima de tombke 6 td ien t synchrones dans ies deur rudsseaux, l e s deux

ann&es. I 1 se pour ra i t que ce para~n&"ir ssoit r e l i k au temps e t aux rnarhes. La dur6e de l a v ie l a r v a i r e

@hait de 22 jours en 1963, mais, en 1964, i l sernble qu%elle n ' a i t 4 t6 que de 15 jours , ce cjui a u r a t i pu e l r e

cads6 par 1 ' a r r iv6e de larves plus v i e i l l e s dont on ne connaissai t pas l e s ant6cGdents.

Les c o q u ~ i l e s c o l l e c t r i c e s chang6es deux f o i s par rnois se sont a ~ E r 6 e s s a t i s f a i s a n t e s pour deq contrdles

rggul ie r s de l a tomb&? du naissa-in, mais el ' ies n'6taaien-t pas assez exactes pout l a a6 temina t ion des maxima de

f i x a t i o n . Lhut i l i sa t ion de plaques d'amiante a donni? des r 6 s u l t a t s i n f e r l e e r s 5 ce qui avaient 6t6 obtenu avec

l e s coqui1Tes de p&ronc?es, ~ a i s e l l e nken P t a i t pas moins ad6suate pour l a co13ecte du naissain.

tdots ~ 1 6 s : Hukre , Crassostrea v i r g i n i c a , l a r v e s , v6l iggres , tomb& du nai s s a i n , populations, mortal i t6 . ----

Tile p r c i e n t r epor t is t h e I,isi In t he i r r i e s o f annual r e p o r t s aen t loned LKI tile p r e f d ~ e , diid i t d e a l s w ~ t l l t h e d e s c r r p t l o n of t h e p o p l a t l o n s o f o y s t e r l a r v a e 1r1 Dldeford Rlver du r ing t h e summer of both 1963 and 1964, I t s f o n a t is s l m l l a r t o t h a t of t h e p rev lous f l v e r e p o r t s (Drlnnan and S ta l lwor thy , 1978, e t seqy ) and it fol lows average concen t ra t rons o f t h e varrous r e c o g ~ i s a b i e s t a g e s , t h e i r m o r t a l r t y and/ o r r ec ru i tmen t , and t h e accompanyrng s p a t f a l l s . I n a d d r t l o n , t h e t o t a l popu la t ion of Mature l a r v a e and t h e t o t a l ca t ch of s p a t w i l i be r ep resen ted by day- larvne/lOO l r t r e s o r d a y - s p a t l s h e l l , f o r purposes o f b e t t e r comparison k i t h t h e popula tzons o f preceding y e a r s T ie s e t t l n g q l io t l ea t an3 t h e s e t t r n g index f o r each y e a r will a l s o be glben t o a57lst I n t h e s e comparisons The r e l a t i o n s h ~ p Setbeen t h e concentra- t r o n s o f Mature l a r v a e i n t h e water and t l ie l n t e n s l t y o f t h e s e t t r n g process w l l l he examlned t o a s s e s s t h e accurzcy o f s p a t f a l l p r e d l c t l o n .

Three t e s t s o f s p a t co l l ec t io r l e f f r c i e n c y were c a ~ r l e d ou t I n 1963 and 1964 [I) Smelt Creek was compared inbo th yea r s h r t h Paugh's Creek f o r s p a t f a l l ~ n t e n s i t y by non i to r lng s p a t f a l l I n both . E a r l i e r experience had lnd rca ted t h a t t h e r e may be l a r g e d l f - f e r e n c e s between t h e two a r e a s . (2 ) S h e l l s changed o n l y bimonthly but kith ex insu res overlapping by one week were compared w i t 1 1 t h e u i u a l procedure f o r moni tor ing s p a t t a l l [ I I I 196.3 only) . (3) Commercial a s b e s t o s boar2 has compared rrrth t h e 5cd l lop s h e l l a s a c o l l e c t o r m a t e r i a l ( r n 1904 on ly ] .

Figure 1. The coas t o f P r ince Edward I s l a n d , Canada, from Cascumpeque Bay I n t h e no r th t o Malpeque Bay i n t h e sou th , showing t h e l o c a t l o n o f Bldeford River (shaded)-- the a r e a sampled i n t h e p resen t s e r i e s o f obse rva t ions , 1958 t o 1964.

-- -

Figure 2. Rideford River, P . f . I ., showing l o c a t i o n s of va r ious sampling s t a t i o n s and a r e a s . cor:tours drawn

from sounding5 taken rn 1958.

Slnce t h e precedrng r epor t s rn t h t i s e r i e s have given d e t a i l e d d e s c r i p t i o n s o f t h e techniques adopted, (See Drinnan and S ta l lwor thy , 1978 e t seqq.) only technical changes o r i nnova t ions w x l l b e men- t roned h e r e . One change concerned t h e s e p a r a t i o n of t h e two l a r v a l s t a g e s Late S t r a i g h t Hlnge from In- c r p l e n t Uinbo, and one I n iovat ion was a iiivre accura t e method o f f r a c t r o n a t l n g t h e spat -count on a heav i ly s e t s c a l l o p s h e l ; . Both o f t h e s e were lntrodliced i n 1963

I h e e s tua ry t o he s tud red was a s be fo re , Ilide- f o l d R ive r , i' E 1 r ~ g l i r e 1 showi t h e l o c a t i o n of t h i s a r e a wl t l l i r~ p r i n c e Edward I s l and ?he l a r g e s c a l e map An r i g u r e 2 grves J more d e r a i l e d map of t h e e s t u a r y and has l a b e l l e d t h e p a ~ t l c r ~ l a r loca- tlon.; sampled.

' f ie p a t t e r n of sampling had now been s t anda rd - r sed t o mo-ring samples only , and o f t e n t h e f i l t r a t e from t h e t h r e e l e % e l s (it, 4 ' , 7 ' ) was pooled on one f l Z t e r . Sairrples were t h e r e f o r e always c r u r s l n g and sometlines pooled and sillrctzmes sepnr:lte (i . e . t h e t h r e e l e v e l s kep t s e p a r a t e ) . ilere :ire tile p a t t c r n s used.

Level, Pooled ( f e e t Amount o f

Area o r from Water Year Sampled Sepa ra t e Surface) Pumped ( g a l . 1 - ----- 1963 81-52 poolec l i , 4 ' , 7 ' 75 J u l y 2- Aug. 19 R l - B 2 s e p a r a t e 1' 25

1) 1 pooled I \ 4 ? , 7 " 7 5

1964 J u l y -- kug. 17

i' l ?ooled 1" 4 ' , 7' 75

in each y r ' i r t h e s e t of samples a s shown was taken two t o t h r e e tiiir,es a week through 6 o r 7 weeks dur- i n g J u l y and p a r t o f Augusr a s given above. S tages recognised were t h e same a s i n previous years.

I, EH TI, Lti

1x1, I U - - I J , li

~ bl

On J u l ) l C , 1363 a s l i g h t change rn the c r i t e r l a o f r ecogn l t ron of t h e s t a g e s Lii and Ili was rn t roduced such t h a t t h e r e k r l l be somewhat fewer LH and more TLI t h a n p r e v i o u s l y . Unfor tunate ly no more p r e c i s e ln fo rma t lon on t h l s change was recorded. There a r e , o f cour se , t r a n s r t r o n f ~ m s between a l l s t a g e s a s they develop rn sequence and ~t i s a problem when count ing t o decrde how t o s e p a r a t e them s h a r p l y . There w i l l always be a zone be ~t narrow o r wide, between any two a d ~ a c e n t s t a g e s when t h e coun te r w r l l ha>e t o a s s i g n t h e organisms a l t e r n a t e l y t o t h e s t a g e below and t h e s t a g e above, The change noted above concerns t h i s "zone o f u n c e r t a ~ n t y " on t h e LFI-IU boundary.

I n 1963 t h e usual s c a l l o p s h e l l t ype c o l l e c t o r s wi th s h e l l s a t 1 ' , 4" and 7 ' d e p t h s were s e t up and monitored i n both Smelt Creek and Paugh" Creek. Locations a r e l a b e l l e d PA, SA, i n Figure 2 . I n o rde r t o provide a use fu l comparison wi th previous p r a c t i c e i n t h e f i e l d s t a t i o n s , bimonthly s h e l l s were run a t both t h e s e p o i n t s a s wel l ( l a b e l l e d PB and SB). Bimonthly s h e l l s b e r e mounted i n p a i r s and one of each p a i r was changed each week, s o t h a t t h e exposure t ime o f each s h e l l overlapped by one week both t h e s h e l l s e t one week e a r l i e r and t h e s h e l l s e t t h e following week. The arrangement reduced count ing work and s t i l l p re sen ted reasonably f r e s h su r faces i n case fou l ing was seve re .

In 1964 t h e same two s t a t i o n s were monitored by r o u t i n e c o l l e c t o r s with s h e l l s a t l ' , 4 ' , and 7 ' . I n a d d i t i o n a t each s t a t i o n t h r e e a sbes tos board squares were a l s o used i n t h e same way a s t h e s c a i - l op s h e l l s . Squares were 4" x x4"' x k " . This allowed a comparison of t h e two m a t e r i a l s a s c u l t c h . Both types were changed d a l l y .

F rac t iona l Counts o f Spat on Sca l lop S h e l l s

Mr. i i . It, l'ayne suggested the u5e 0 5 sectcirs i n counting orlly p a r t of t h e s p a t on a heav i ly i e t s c a l l o p s h e l l . The procedure i s fo l low- F ind t h e c e n t r e o f t h e s h e l l a c c u r a t e l y . A t r m s p a r e n t p l a s t i c over lay wrth c o n c e n t r i c c i r c l e s on it i s an easy s a y t o do t h i s Draw t h e dlameter which passes through t h e mzddle of t h e h lnge. Draw ano the r d lameter s o a s t o c r e a t e two s e c t o r s o f appropriate s l z e s o t h a t a l l s p a t I n both may reasonably be counted. The angle chosen determznes t h e s l z e o f t h e f r a c t i o n counted and i f t h e angle i s a c c u r a t e l y drawn % i t h a s e t square t h e count w i l l be a f a l r sample of t h e a r e a s o f concen t ra t ron roonil t h e hinge and In t h e c e n t e r of t h e s h e l l , a s well a s o f t h e more spa rce ly s e t t l e d l l p a r e a . An ang le of 900 wouid r e s u l t r n count lng $ t h e s h e l l , 4 i0 In 22.50 l n 1/8, and so on,

RESULTS AND DISCUSSIOV

The p rogres s of t h e development o f t h e o y s t e r l a r v a l popu la t ion f o r t h e two yea r s i s shown 1-i

Flgure 3 (1963) and i n Figure 4 (1964) Irt t hese f l g u r e s average concentra tzons f o r every day when samples were taken have been p l o t t e d semi loga r i th - mzcally a s well a s I n accurnulatl~re pe rcen tages . The d a t a from a h ~ c h the) were p l o t t e d a r e given i n f u l l In Appendices I and ?I. I n Tables 1 and 2 a r e shown t h e d a i l y averages and t h e l r corresponding accumulative percenrages a i a c t u a l l y p l o t t e d i n t h e f l g u r e s . b e r a g e s p a t f a l l s i n s p a t p e r s h e l l p e r day f o r both Paligh's Creek and S n e l t Creek a r e a l s o p l o t t e d i n Flgure 3. S p a t f a l l i n Figure 4 1s de- r n e d from s t a t z o n SA i n t h e conf luence o f t h e two

Figure 3. Gomposite p l o t sllowlng average l a r v a l concen t ra t ions throughout t h e summer o f 1963. The upper graphs s h o ~ t h e p ropor t ion jkj o f each l a r v a l s t a g e I n t h e t o t a l sample f o r each day sampled. ";he lovder graphs a r e semilogar l thmic p l o t s o f average concen t ra t lons I n l a r v a e p e r 100 l i t r e s Sca le s f o r va r lous s t a g e s a r e s h i f t e d f o r c l a r i t y . The s p a t - f a l l graph 1s I n spa t p e r s h e l l p e r day.

2

j Spat

June July Tot at E H

i I

PaugKs o 1 C r e e k

I

July A u p

Spot M

July A@g

Table 1 . Represec ta t ive average 1arv;rl concentr t i t ions i i i l a rvae pe r 100 l i t r e s and accrirnulative pe rcen tages , 1963. Upper f i g u r e i s average l a rva1 concen t ra t ion . Lower f i g u r e i n each e n t r y 4s accumtilative percentage

Dates To ta l EH Lti I U U M

2/7 25.5 21.8 3.6 85 .7 100.0

Creeks . 1.~11 s p a t f a l l d a t a appear i n Appendix I I I LARVAE iut 'D SPATFALL, 1963 a!id I\.

Iil gene ra l , t he popu la t ion o f 1963 was wrch more numerous than t h a t o f 1964. I n 1963 spawning kas e a r l i e r , concen t ra t ions h ighe r , and s p a t f a l l h e a ~ i e r than i n 1964. Figures 3 and 4 show these f e a t u r e s . Fu r the r d e t a i l s a r e given below.

Figure 4 . Conposlte p l o t showing average l a r v a l c o n c e n t r a t i o n s throughout t h e s m e r o f 1964. The upper graphs show t h e p ropor t ion ( ' 0 ) o f each l a r v a l s t a g e i n t h e t o t a l sample f o r each daj s azp led . The lower graphs a r e semilogar i thmlc p l o t s o f average concen t ra t ions i n l a r v a e p e r 100 l i t r e s . Sca le s f o r va r ious s t a g e s a r e s h i f t e d f o r c l a r i t y . The s p a t - f a l l graph i s I n s p a t p e r s h e l l p e r day.

Larvae were f i r s t seen on J u l y 2 and average c o n c e n t r a t ~ o n s reached n e a r l y 10,000 l a r v a e p e r l i t r e s on J u l y 12. On t h ~ s day a l s o t h e h rghes t In- d i v i d u a l t o t a l count was recorded, 17,248 l a r v a e p e r 100 l i t r e s . Although no t a r eco rd , t h i s 1s a very high concen t ra t ion f o r t h e a r e a . On J u l y 16 a heavy s e t was p red ic t ed f o r J u l y 24 and t h e days fo l lowing . Th i s proved accura t e , and by August 1 s e t t i n g was v i r t u a l l y over . The l a r v a l concen t ra t ion decreased s t e a d i l y from J u l y 12, and t h i s i n s p i t e o f a small spawning b u r s t about J u l y 25. The s p a t from t h i s b u r s t was s c a r c e l y d e t e c t a b l e .

S p a t f a l l remained above one s p a t p e r s h e l l p e r day from J u l y 20 u n t i l August 2 . A r e l a t i v e l y heavy s e t occur red i n Smelt Creek and i n Paugh" Creek a t

l a b l e 2 , Larval Population I n 1964. Represen ta t i ee Averages (Larvae p e r 100 l i t r e s ) and accumulatlve p e r c e n t -

Dates 'Total tiil I l l T ll II M .- --- .. - -- - - - - -

t h e same t m e , J u l y 26 t o 29, when one i h e l l c a r r i e d 4680 s p a t . T i e average s p a t p e r she11 p e r day, how- e v e r , reached a peak of on ly 762.

S p a t f a l l d a t e s can be p r e d i c t e d from t h e peak concen t ra t ions o f Eli and t l l l a r v a e observed or. J u l y 20. %ese s t a g e s would be expected t o s e t In about 17 days and t o produce a peak i n s p a t f a l l on August 6 . The observed peak i n s p a t f a l l was, however, ove r t h e week-end o f J u l y 31 t o Psigust 3 . Severa l expla- na t ions a r e p o s s i b l e f o r t h i s d i sc repancy . (a) The l a r v a l l i f e pe r iod was a c t u a l l y shor tened i n 1964 I f so , it was only J u l y 17 ( I n f e r r e d spawning) t o August 1, o r 15 days. Since t h e average water tem- p e r a t u r e dur ing t h l s t ime was only 21.4oG. any s h o r t - ening would have t o come from o t h e r causes , l i k e i n - c reased fcod supply . (b] The s e t t i n g peak was neve r f u l l y expressed, but c u t s h o r t by some a d ~ e r s e c i r - cumstance which prevented s e t t i n g o f many l a r v a e . The s p a t f a l l curve suppor t s t h i s suggestion by i t s r a p i d dec rease throughout August. ( c j The l a r v a e which s e t dur ing t h e observed peak on Ju ly 37 t o 4ug- u s t 3 Nere no t seen dur lng t h e ~ r younger s t a g e s bu t

0

In 1963 PaugIlts Creek. sllows a consistently h e a v i e r s p a t f a l l t han Smelt Creek even though t h e t i ining was synchronous. Th i s may be seen from t h e graphs o f Figure 3 and from t h c a c t u a l coimts given i n Appendix 111. T h ~ s compar isol~ xi11 be explored f u r t h e r a f t e r cons ide ra t ion o f t h e 1964 d a t a .

LARVAE AND SPATFALL, 1964

Larvae were not seen u n t i l J u l y 14 I n 1964 and t h e h i g h e s t concen t ra t ion observed was 2913 l a rvae / 100 1. on J u l y 27 I n Paughls Creek. On t h e same day was recorded t h e h i g h e s t d a i l y average o f 2002 larvae/100 1. A f t e r August a l l s t a g e s were i n s t e a d y d e c l i n e .

Table 3 . Comparisoi~ of 1963 and 1964 Larval Popula- t i o n s and S p a t f a l l s . -----

Rat io 1963 1964 1963/64

Larvae f i r s t observed 2/7 14/7

Average water temperature 3/7 1317 reached 20°C

Concen t ra t io~r peak 12/7 27/7

S p a t f a l i peak 26-29/7 31/7-3/8

Lengl~t of l a r v a l i i f s 22 days 15 days

j)3;;- (-113::al) 102,073 25,540 3.85 p e r 100 l i t r e s

Day - lai-i7ne (!.ia";tirc) 3,730 969 3.85 p e r 100 l i t r e s

Day-spar per s h e l l 1,729 321 '5.56

~ e n t = S e t t i n g quot ' 2.16 3.12 0.69 Day-larvae (Mj Day- ; p a t / s h e l l

S e t t iilg index = 4 6 . 3 32.1 1.44 Dsy-spar /s l ie l l :i I00 Day - l a rvae (MI

came i n t o t h e a r e a froin elsewhere be fo re s e t t i n g , i . e . t hey were ' k e c r u i ted" . Support f o r t hese a l t e r - n a t i v e s will be sougilt a s t h e d i scuss ion proceeds .

To compare t h e l a r v a l popu la t ions o f 1963 and 1964 *it11 each o t h e r and wi th those o f o t h e r years e s w e l l , some g e n e r a l l y r e p r e s e n t a t i v e f i g u r e s a r e u s e f u i . The t o t a i iaagnitude of t h e l a r v a l popula- t i o s (or any d e s i r e d s t a g e ) may be r ep resen ted by t h e o r e a j s ] under t h e curves o f i:ignres 3 and 4 . Tliese will be i n day-larvae/lOO 1 . S i m i l a r l y t? le a r e a under t h e s p a t f a l l curve w i i l be i n d a y - s p a t / s h e l l . 'These q u a n t i t i e s w i l l i n d i c a t e good and bad spawn- filgs and good and bad s p a t f a l l s . To compare s p a t - f a l l .wit:? t h e riunibers of Mature l a rvae which produce i f , t h e s e t t i n g qu3t ie i r t

day- l a r v a e (Mature) / lG0 1. da)--spat/shei 1

i s a ineastire o f t h e ~lwrnber o f l a rvae r e q u i r e d t o p ro - dace one s p a t , whi le t h e s e t t i n g index

d a j - s p a t / s h e l l x 100 -- day- larvae (Mature)/100 1 .

i s a measure o f t h e rrwnber o f s p a t produced p e r lar -va , o r s e t t i n g e f f i c i e n c y . 'These and o t h e r char- a c t e r i s t i c s o f t h e l a r v a l popula t ions o f t h e two y e a r s a r e g iven i n Table 3.

When t h e s e t t i n g q u o t i e n t approaches 1 .0 ( s e t t - i n g index)= lOOj an e x c e l l e n t s e t of s p a t i s i n d i - c a t e d . X coimrerciaily success fu i s p a t f a l l r e q u i r e s , o f cour se , adequate numbers t o begin wi th and good s u r v i v a l o f t h e s p a t themselves. The q u o t i e n t ( o r i ndex j measures only "ihe c o r r e l a t i o n between s p a t - f a l l and t h e concen t ra t ion o f n a t u r e l a r v a e . The +.,- ,i,, ~ ~ , , , , r t i c s , *.,on+ - s e t t i n g q u o t i e n t a i d s e t t i n g index a r e r e c i p r o c a l s o f each o t h e r and t h e r e f o r e both con- t a i n t h e saiirr i irforniaiion. Which i s used i s merely a m a t t e r o f convenience.

Timing of even t s i n 1965 was much e a r l i e r than i n 1964. The d a t e s o f t h e f i r s t observed l a r v a e and t h e peaks i n l a r v a l concen t ra t ions were d i f f e r e n t i n t h e two yea r s by 1 2 t o 15 days . These conspicuous d i f f e r e n c e s , shown i n Table 3, c o r r e l a t e we l l w i th water temperatures i n t h e two y e a r s . Average wa te r temperatures (based on 2 s u r f a c e and 2 bottom read- ings p e r day) reached 20nC. on J u l y 3 i n 1963, and be fo re t h a t d a t e af ternooi i r ead ings were above 2WC f o r a few days . 111 1964 t h e 20°C. average was reached on , ) u ly 13, wi th af ternoon readings above 200C. s i n c e J u l y 9 . Both yea r s showed a sccond major spawning b u r s t . In 1963 i t cane 20 days a f t e r t h e f i r s t and i n 1961 only 10 days l a t e r than t h e f i r s t . Very l i t t l e s p a t f a i l r e s u l t i n g from these second b u r s t s was seen i n e i t h e r yea r . Temperatures were doub t l e s s determining t h e s e seconilnry b u r s t s t o o , thro-~igh t h e i r inf luei ice on t h e r ipen ing p rocess and hence on t h e p ropor t ion of tire o y s t e r popnlntioi: t h a t achieves spawning r ead iness ax any g i v e n time. ?he warmer temperatures o f 1963 musc 11ave prepared a l r i rger p ropor t ion o f t h e a d u l t s f o r spawning earl:, s i n c e t h e peak l a rva l ronc-e i~t ra t ions were reached only 9 days a f t e r t h e water reachcd 20W:., while i.11

1964 t h e peak concentra t ior ; was riot reached ~ r n t i l 14 days a f t e r t h i s event even ti~origli t h e tcmpe,, *'ituro was above 20oC. a l l t h a t t ime. l?lis i s c l e a r i n d i - c a t i o n t h a t i n 1964, many u d u l t s were n o t , a t f i r s t , ready t o spawn.

S p a t e a l l peaks do rrot fo l low the l a r v a l p a t t e r n . In s t ead o f rnaintairiing t h e i n i t i a l t ime d i f f e r e n c e o f 12 t o 15 days shown by t h e l a r v a l popu la t ions t h e d a t e s of t h e s p a t f a l l peaks a r e on ly ahoct 5 days d i f f e r e n t from one yea r t o t h e n e x t . This has r e - s u l t e d i n a g r e a t d i f f e r e n c e i n t h e apparent l eng th of l a r v a l l i f e , 22 days i r ? 1953 and on ly 15 da;ys in 1964. Temperature r eco rds show no r i s e i r i tempera- t u r e i n 1964 t o account f o r t h i s shor tened l i f e span. I n f a c t temperatures were iliuch h ighe r i n 1963 than i n 1964.

S p a t f a l l p r e d i c t i o n i n 1954 was not i n i t i : i i l y a c c u r a t e when based on t h e e a r l y l a r v a l s t a g e s . Neverrheless a t t e n t i o n r e t h e l a t e r s t a g e s gave warning o f tile e a r l i e r s e t .

The t o t a l l a r v a l popula t ion of I963 was 3.85 t imes a s l a r g e a s t h a t o f 1964 [Table 3 ) . ?%is r a t i o h e l d even whon only mature l a r v a e a r e con- s i d e r e d , whick strows t h a t tlie growth o f l a rvae i n both yea r s was about equa l ly success f r i l . S p a t f a l l i n 1964 was, however, l e s s s i ~ c c e s s f u l a s r e f l e c t e d by d a y - s p a t / s h e l l , s e t t i n g q u o t i e n t , and s e t t i n g index i n Table 3 ,

S p a t f a l l does n o t always c o r r e l a t e wlth t h e concen t ra t ion o f mature l a rvae Fn t h e warer I f co r re l a t lo r l were p e r f e c t t h e s e r t l i l g ~ n d e x (and t h e s e t t i n g quor l en t o f course) hould i-enlain cons tan t from p l a c e t o p l a c e and f ron yeax t o y e a r Another example o f t h l s 1 s seen when t h e r e s u l t s from t h e two c reeks a r e compared.

S p a t f a l l i n Smelt Greek and Paug11's Creek

The day- larvae (Matare) f o r t h e two c reeks and f o r both yea r s a r e compared i n Table 4 where t h e day- spa t p e r s h e l l a r e a l s o given. S e t t i n g y a o t l e n t s and s e t r i n g Ind ices a r e c a l c u l a t e d . The 9 ighes t concentrations o f mature l a rvae a r e found ~n Paughfs

Creek I n both yea r s , and y e t t h e s p a t f a l l i s g r e a t e l i n Paugh" Creek i n 1963 and r n Smelt Creek i n 1964 ( s t r i c t l y speaklng i n B1,R2) Thrs i s a d l s t r n c t break i n c o r r e l a t i o n betbeen i a r v a l concen t ra t ions and s p a t f a l l s . Where t h e s p a t f a l l was good (Paugh's Creek 1963, and Smelt Creek 1964) t h e s e t t i n g i n d i c e s a r e ve ry c l o s e . They a r e a l s o c l o s e i n t h e poorer p a i r They do shob, however, a s t r o n g difference between t h e two c reeks i n e l t i l e r yea r . Th l s r e f l e c t s and empltaslses t h e break I n c o r r e l a t r o n . Other f a c t o r s a r e , t h e r e f o r e , h l g h l y s l g n l f i c a n t i n d e t e r - mrning s e t t l n g r n t e n s l t v than mere11 t h e concentra- t r o n o f Larvae p resen t

Table 4 . Compar~son o f Paugh" Creek and Smelt Creek popu la t ions o f l a r v a e and s p a t . *kote : Smelt Creek d a t a f o r 1364 a c t u a l l y were taken on ly i n Areas Bi,B2.

1963 1964

Smelt Paugh's 'Smelt Paugh's Creek Creek Creek Creek

Day- l a r v a e (Mature) 35 17 4453 629 1294 p e r 100 l i t r e s

Day-spat p e r s h e l l 628 2831 354 268

S e t t i n g quor i en t 5 .6 1 .57 1 .56 1 . 0 7

S e t t i n g index 17 .8 53.6 56 .2 20.7

V e r t i c a l d i s t r i b u t i o n of s p a t

The s p a t f a l l d a t a f o r 1963 conflrm t h e usua l p r e f e r e n c e o f s e t t i n g l a r v a e f o r t h e lowest s h e l l {Appenalx 111) I n 1963 (Appe~ldix I\) t h e heavres t s p a t -ias found on t h e 4 ' s h e l l Thls 1s f u r t h e r evidence of t h e a c t i o n o f some d i s t u r b i n g f a c t o r ( s 1 I n t h e setting process In 1954 I n Paugh's Creek

Accuracy o f s p a t counts

When a s h e l l has more than 100 s p a t , only a traction need be counted Payne" mcthod giver1 a b o ~ e (page 2 ) g ives an a c c u r a t e subd iv i s ion and t a k e s I n t o account both the a r e a coullted and t h e tendency o f zhe s p a t t o favour t h e h ~ n g e a r e a of t h e s h e l l . Althouglt no s t u d i e s have been done t o ob ta ln a measure o f t h e accurac) of t h i s method, i t i s c e r - t a l n l y rnuch laore pxecxse thail t h e var ia txon i n t h e s h e l l s themselves , 1 e fron, 4"to 5" i n d iameter ox 12 t o 20 1nchei2 i n a r e a To j u s t i f y P a l n e t s method t o l e r a n c e s l n s h e l l s l z e 5hould be tightened. Tills may n o t be worth whrle because we a r e i n t e r e s t e d I n s p a t f a l l s t h a t vary by nore than 1000-fold. We have n o t , t h e r e f o r e , s e l e c t e d t h e s h e l l s r z e s used a s c o l l e c t o r s .

Mortality and/or r ec ru i tmen t wi th ln t h e l a r v a l populations o f each year a r e shown i n Flgures 5 and 6 . An example o f t h e c a l c u l a t l o n s from which t h e p o i n t s i n t h e s e graphs were d ~ r i v ~ d 15 glven i n Table 5 . I t a p p l i e s t o 1963 d a t a . The c a l c u l a t l o n s have been desc r loed I n d e t a l l 10 Drinnan and S t a l l w o r t h y (1958).

0 5 10 15 20 25

D o y r f r o m Spawning

Figure 5 . "Mortali ty" o f che t o i a l 1963 l a r v a l o y s t e r popu la r ion . The graph g ives e s t i - mated t o t a l q u a n t i t i e s o f each l a r v a l s t a g e which could have con t r ibu ted t o t h e observed s p a t f a l l s . A r i s i n g graph i n d i c a t e s e i t h e r an i n c r e a s e i n sampl- i n g e f f i c i e n c y o r e l s e r ec ru i tmen t o f popu la t ions no t p rev ious ly sampled. Mor ta l i t y i n % p e r day may he judged by comparing downward s l o p e s wi th t h e s t r a i g h t l i n e i l l u s t r a t i n g t h e s lope o f 10% p e r day.

The interpretation of t h e s e graphs r a l s e s some l n t e r e s t l n g ques t rons . (1) In a l l graphs t h e quan- t l t y o f Late S t r a i g h t Hlnge (Lfi) l a r v a e i s g r e a t e r than t h a t o f t h e Ear ly S t r a l g h t tjxnge (ZH) from which they a r e supposed t o have a r l s e n by normal growth p rocess . As i n previous y e a r s , i t i s c e r t a l n t h a t t h e filters used d i d no t r e t a i n a l l t h e LH l a r v a e . I t 1 s probable t h a t t h e ext remely patchy d l s t r l b u t i o n o f t h e e a r l y l a r v a e p reven ted our pumps from encountering a l l o f them. Both t h e s e f a c t o r s would cause t h e q u a n t i t y of LH t o exceed t h a t of t h e EN I n t h e absence o f such c o n s l d e r a t l o n s a p o s i t l + e s l o p e i n these graphs l n d l c a t e s r ~ c r l ~ ~ t m e n t

(21 Recruitment i s c l e a r l y shown between LH and I n c i p i e n t Umbo ( i U j i n 1963. Th i s i s indeed sug- ges t ed by t h e graphs o f Figure 3 where t h e r a p i d changes be fo re t h e 1 s t J u l y i n t h e percentage p l o t i n d i c a t e t h a t d i f f e r i n g water masses a r e being sampled on success ive days . The same even t s can bc seen i n t h e semilogar i thmic p l o t i f somewhat l e s s c l e a r l y .

(3) Mor ta l i t y i s i n 1963 (Figure 5) about 10% p e r day from I U t o Mature ( M j , a s can be seen by comparison wi th t h e 10% l i n e supp l i ed . I n t h i s c a l - c u l a t i o n , l o s s by death ( t r u e m o r t a l i t y ) i s i n d i s - t i n g u i s h a b l e from l o s s by d i l u t i o n o r mig ra t ion .

'if m i 0 N 1 0

ol ri Oi Ln N m

sane time i n both c reeks . So recrui tn ient must have occurred i i i llotlt, and must have been coun te rac ted i n Smelt Creek and 61,B2 by simultaneous l o s s e s .

Smelt Creek

Frgure 5. '%Mortiill ty" o f s e l e c t e d segments from I964 l a r v a l o y s t e r population. S imi la r t o I ' igure 5 . Graphs l n c l u d e a l l antecedent l a rvae be fo re t h e da te s shown a t t h e r i g h t .

( I ) I n 1964 t h e graph ( i l gu re 6) l a b e l l e d 7/8/64 i n c l u d e s t h e an teceden t s o f a l l t h e spa t observed, and shows a m o r t a l r t r approaching 2 0 % p e r day, except f o r some rec ru i tmen t o f M l a r v a e . In vrew of e a r l l e r d lsc i issronq [Drinnan and St , i l lwor thy, 1978) o f t h e possible upstream t r a n s p o r t o f any l a rvae t h a t t end t o remain iii t h e deeper l a y e r s , t h1s recrui tment seem.; t o he a l i k e l y event ,

(5) Ihe graplii I , l bc l l e i~ 17/8/64 i l i g n l e 0 ) ~ o i i - t a t n i t h e intecedcrits of t i ~ o s e l a rvae r e i i r l t lrig from tl ic c a i l y s p a w ~ i n g b u r s t \ i i i both i'a~iglr' 5 i reek and I n Smeit Creek ( o r jt I ~ , i i t I n t h e 'Ireas 131,132). Pa~igir' i Creek has gained many I U l a rvae whr l e t h e morta l l t y o f t h e Umbo (li) and t h e M a7,e lO0* p e r day o r l e s i . a o s e from B1,132 show recrui tment only I n E.1 s t a g e .

Retunl ing t o t h e v a i i d l t y o f t h e s h o r t (15 days) l a r v a l i r f e span implled by t h e graphs o f Figure 4 , a r e a l r l s e i n growth r a t e cannot be e n t i r e l y ru l ed o u t . Such a very s h o r t l a r v a i l l f e was o b s e r ~ e d by Medcof (1939) and a t water temperatures o f 19-20oC., 1 . e . c l o s e t o t i lose of tire cool st:nmel- of 1964

l rom iippei~dlr l V ~t is ~ i e ' l r t h a t a \ b c \ t o i board a t t l a c t s l e s s t l la~i 1/10 its mariy spa t as (lo i c a i l o p s h e l l s . Never theless t h e a sbes tos does r e f l e c t f a l t h F ~ l l y both t h e s e t t i n g peaits and t h e usua l ve r - t i c a l p re fe rence .

BIMONTHLY SHELLS AS SPAT COLLECTORS

Bimonthly she1 1s o f 1963 have l e g r s i e r e d tile peak of s p a t f a l l f a r t h f i l l y , bu t ~ t s tlrnlny i a n a o t he l d e n t i f r e d wlrh p r e c ~ s ,on (A~lpendix I l I i Ope m ~ g b t say t h a t good s h e l l s whose pe r iods o ~ e r l a p w i t t i loh c a t c ? ~ \ h e l l s must have caught wel l dur ing the uriover1,~pped part o f t h e l r tlshizli: pe r lnd i n t h r s way t h e p o s i t i o n o f t h e peak could he narrowed some- w h d ~ , but l t s l o c a t i o n would be l e i s a c c u i a t e than ~f s h e l l s were changed d a l l y The method kould be a good low-cost monltorlng dev ice w h e ~ e accoraci o f t lmlng 1 s o f l e s s zmportance. C lea r ly , counts would be somewhat in f luenced by any p o s t - s e t t l n g m o r t a l i - t i e s .

WEATHER AND WATER

Spawnlng and s e t t l n g a r e inflriericed 1,) iur round- l n g conditions. Some c o r r e l a t i o n s a r e d ,scernabie h e r e . I n 1965 t h e days o f .July 3, 4, 5 , arid 7 each had a long low t l d e occurring througl-iout t h e day -

l l g l i t hours s o t h a t t h e sun could warm t h e mud f l a t s Th i s was no doubt t h e cause o f t h e r i s e rn k a t e r temperatures which caused t h e spawning. In addi- t i o n 2.74 inches o f r a i n f e l i between J u l y 2 and J u l y 12, The p o s s i b i l i t y cannot be i.gnored t h a t t h e r e may be connection between r a i n run -o f f and t h e spawning o r s e t t i n g s t i m u l i . The s e t t i n g " s t r i k e " occurred ove r a week-end s o t h a t weather r eco rds a r e meagre. From J u l y 24 t o 29, 0 .97 inches o f r a i n f e l l , 0 . 2 inches o f it on J u l y 2 9 on a g e n t l e e a s t - e r l y wind which suggests t h a t some o f t h e week-end was a l s o cloudy although no t r a i n i n g .

Robert R. Payne had f u l l r c s p o n s l b r i r t i f o r t h e ope ra t ion o t a l l phases o f t h e program In 1963 and 1964 l n c l u d ~ n g t h e count ing o f l a r v a e anti o f s p a t and t h e r n l t i a l c a l c u l a t i o n s . He had t h e he lp o f K . Roy Oatway i n t h e operation o f boa t s and gea r

Against t h e s11oi.t i:ir.v;! l I if:. and i 11 f;ivour of an exciiange o f water masses, is t h e ten~porary disnp- pearance of n e a r l y a11 El l and Lfl l a rvae on ,July 27 (See pe rcen tage graphs , Figure 41, and t h e l a r g e ,.-rr-n~nro p,,,,A,L,g, o f I U l a r v a e sudden ly presen t i n s t e a d . The m o r t a l i t y graphs i n Figure 6 r e f l e c t such r e - cruitmcllt only i n t h e Paugh's Creek graph where it i s v e r y s t r o n g . The s p a t f a l l occur s , however, a t t h e

Drinnan, R . E . and W . B . S t a l lwor thy , 1978. Oyster popu la t ions and assessment o f s p a t f a l l , Bideford River , P . E . I . , 1958. Fish . Mar. S e r v . , Tech. I n p r e s s .

Nedcof, J . 6 . . 1939. Larval l i f e o f t h e o v s t e r [Os t r ea v l r g i n l c a ) ~n Bideford River . I r s h . Res. Rd. -- Can. 4(4) : 287-301.

- - - - - 1961. F u l l e r exp1o:tation of natural s p a t - fall. 1;. R . A . O r ig . MS., Biol . S t a t i o n , S t . Andrewi, No. 932. (unpublished MS.)

Appendix 1. 1963.

h i g h

I

u -- 0 i c w YI ffl O W h a m

C " 7 +J

E ' i - O C l l 4 i-

Quantl tative Counts -- S~zes of i inr each sample two lines are Larval Stages ylven. The flrst line gives the (microns) - rdl~ibers of larvae actually counted. EP 60-84 The second l i n e 1s expressed as LH 84-10C iarkae per I00 litres. I t IS IU ;00-153 under1 ~ned* EU 150-200

LU 200-300

Counts of larval stages seen. 14 >300 1 I

2/7 7 31 (1) 11:30 low 2 5 2 0 2 B 2 1.76 - 0 1.76

- -

2/7 8 B1 (4) 11:30 low 25 18 1 7 1 0 D2 15.87 14.99 0.88 - 0

- 2/7 9 31 17) 11:30 low 2 5 17 13 4 0

2/7 10 P2 P 11:45 low 75 41 36 5 0 (1,4,7) 11.95 10.49 14.6

-- 0 -

4/7 1 7 B1 P 09:30 ebb 75 96 63 33 0 52 (1 A71 28.3 18.7 9.6 0

- -

417 12 B1 (1 ) 09:50 ebb 25 3 2 1 0 82 2.64 1.70 0.88 - 0

4/7 13 B i (4) 09:50 ebb 2 5 14 3 11 0 82 2.64 - 9.39 -- II. -- -- --- ---a -- - -

4/7 1 4 Dl (7) 09:50 ebb 25 63 3 1 32 0 82 55.44 2 2 4 28,z

-- 0 - -- -- - -

4/7 15 P2 P 10:20 ebb 75 632 45 4 177 1 0 (1,471 183.9 132.1 51.5 0.3 0 - - -- - -- . - -

8/7 16 B1 P 13:15 ebb 75 532 24 4 89 21 0 52 (La3?) 157.9 7.0 144.8 6.1 - 0 -

8/7 17 B i ( I ) 13:30 ebb 25 11 7 10 0 0 3 2 9.68 0.88 8.80 - 0 - 0

-- 817 18 31 (4) 13:30 ebb 25 115 3 112 0 0

B 2 101.2 - 2.64 98.56 - 0 - 0

8/7 19 B ? (7) 13:30 ebb 2 5 29 0 9 20 0 82 0 - 48.5 - 0

8/7 20 P2 P 14:00 ebb 75 6 0 3 3 0 i ' i .43 1.74 0

- - 0.87 0.87 0 -

Appendix 1 . 1963.

1017 21 81 P 10:00 high 75 159 108 30 30 0 52 (1,47) 656.88 422.28 117.3 117.3

- - - - 0 -

- -- - -- --

1017 22 I31 ( I ) 10:30 high 25 300 166 78 5 5 1 B 2

764.2 146.08 68.7 - 48.4 0.44 0.44 - --

1017 23 Bl ( 4 ) 70:30 nigh 25 86 12 52 22 0 B 2 757.7 105.7 458 - - - 194 --

0 - --

l0 /7 24 81 ( 7 ) 10:30 high 25 146 29 49 67 0 82 637 - 127 216 - 29 4 --

0 - --

10/7 25 P2 P 11:00 ebb 75 850 81 a 20 16 0 (1,4,7) 2 _ 2 ~ cx 58.2 46.6 e

12/7 27 31 ( 1 ) 11:45 high 25 100 0 45 55 0 I3 2 8800 - 0 3950 - 4850

-- 0 --

12/7 28 B1 ( 4 ) 11:45 high 25 154 0 71 81 2 0 B 2 13561 - 0 6250 - 7135 88 - - 88 - 0 -

72/7 29 B1 ( 7 ) 11:15 high 25 196 1 9 5 100 0 0 82 1 7248 -- 8360 E!? - -- 8800 0 - 0 -

12/7 30 P2 P 11:30 high 75 1222 15 558 6 32 17 0 11 $4,7) 7111

- 87 3247 -- 3678 -- 48.5 - 46.5 !!

1517 32 D l ( 7 1 13:30 high 25 730 6 39 82 3 0 8 2 381 6 176 1145 2407 - - -

-- 4 4 44 - 0 -

15/7 33 B1 (4) 13:30 h i q h 25 108 2 14 85 7 0

15/7 34 81 ( 7 ) 13:30 high 25 120 2 20 9 1 7 0 B 2

7041 ---- '!? 1 173 5346 202 .5 202.5- - 0

75f7 35 P2 P 14:00 h ~ g h 75 120 3 18 88 11 0 (1,471 6895 -- 7 20 1050 -- - 5130 270 - 2 70 - 0

18/7 36 B1 F 0940 ebb 75 122 0 4 5 1 67 0 52 (1,4,7) 3550 0 116 1484 975 975 - 0

18/7 37 D l ( 1 ) 10:00 ebb 25 122 1 14 7 1 36 0 a2 5368 - 44 - 616 3124 792 79 2 0 -

18/7 38 Bl ( 4 ) 10:00 ebb 25 147 1 1 8 9 2 35 1 B2 8624.6 58.8 1055 5398 1026.5 1026.5 -- 58.8

Appendix 1 . 1963

f8/7 39 81 (7) 70:06 ebb 52

1817 43 P2 P 10:36 ebb 75 83 0 0 27 S 5 1 0 ,471 9661 -4

-- C - 31 43 !? - - 3201 3201 116.4

2217 41 51 P 10:30 ebb 75 124 0 O 27 9 3 4 s2 (1,V) 3608.1 0 - 0 - 785.7 - 1353 116.4 - -

2217 42 81 (1) 1k0O ebb 25 99 0 1 2 7 5 8 13 8 2 871 0 - 8.8 - 237.6 2552 255.1 114.4

2217 43 81 14) 1 1 :00 ebb 25 146 0 1 73 65 7 5 2 6% - 0 !!! - - 32.12 1460 1450 308

2217 44 31 (7) i1:OO ebb 25 189 0 14 68 106 1 52 11091.8 - 0 823 3980 -- 3115 S;i75 58.8

22/7 45 P2 P 11:30 ebb 75 97 0 0 18 6 3 16 (1,4,i? 2822.5 !? - 0 523.8 975.5 g 6 % i - 465.6

--

2517 46 81 P i0:OO h ~ q h 75 93 ? 0 23 8 22 30 S2(l94J) 2707 2 9_1 669.2 23Gj 320.2 3211.3

- --- 873 -- - - - - - -- - -- -- --

25/7 47 B1 (19 10:30 h i q h 15 120 17 10 7 46 40 5 2 5 s 74 .& -. 44 3g2> 107 .2 lg-.? 176

.- --- -- -- -- -- -

2517 48 Dl (4) 10:30 high 25 295 0 1 5 1 162 81 82 1297.6 - 0 - 4.4 - 224.3 355.3 -- 356.3

2517 49 B l (7) 10:30 h igh 25 212 2 7 a 8 9 8 5 7 8 2 1865 17.6 61.6 420.24 431 43 1 501 .7 - - - -

-- 2517 50 P2 P 1 1 :DO high 75 106 4 6 22 44 30

jjS4JI 1542 87.3 320 32 436.5 - - 320 -.-- -

-- - 2917 51 Dl P 10:00 flood 75 449 160 200 81 21 7

S2O94J) 1306 487.4 j82 235.7 30.5 30.5 - - - -- 20.38 --

-- p- --- - - -- - - - --

29/7 52 81 (1) 10:30 flood 25 135 I l 70 2 4 15 15 5 2 1188 96.0 616 - 211.2 550 - 66 0 - 132 - --

2917 53 B1 (4) 10:30 flood 25 84 0 1 1 17 26 30 0 2 739.2 - 0 - 96.8 - 149.6 ! I 264

-

2917 54 B 1 (7) 10:30 flood 25 260 46 145 3 1 24 14 B2 2288.1 404.9 - 272.8 0 - 123.2

291755 P2 P 11:00 flood 75 305 R 4 1 61 149 5 0 0,4,7) 1774.2 23.2 238 355 433.5 433.5

- - - 29 1

118 56 Bi P 14:30 low 75 '106 4 54 22 16 10 S2(1 ,421 773.22 23.12 394 160.5 - 58.4 58.4 - 72.8

1/8 58 Bi (4) 15:00 low 25 94 12 64 10 8 0 82 828.2 105.8 - - 564 - 88 - 35.2 35.2 - 0

l /8 59 Bl ( 7 ) 15:00 low 25 157 5 119 17 8 8 B2 2769.6 88.1 299.9 7.04 7.04 -- 14.08

-- --- -- 1/8 60 P2 P 15:30 l o w 75 87 0 26 29 2 2 10

(1,471 840.1 n - 250.3 280.9 105.95 105.95 9 7 -

518 61 81 P 10:00 ebb 75 118 2 16 96 4 0 82 (1,4,7) 343.4 5.82 46.6 279.36 5.82 - 0

8/9 62 131 P 09:45 h i g h 75 119 0 14 9 8 6 1 B2 (1,4,7) 230.86 0 - - - 27.16 190.12 5.82 5.82 1.94

12/8 63 81 P 10:30 f lood 75 175 0 41 121 13 82 (1,471 339.5 0

- - - - - 79.54 234.74 12.61 12.61 0 -

1519 64 B i P 13130 flood 75 228 0 0 1 80 40 8 82 11,471 66-22 0 ? k2.25 5 2 2 5._t2_Z2 2.32 ---- -- - - - - - - . --- - - .- - - - - - - - - - - - .- - - - -. - - --- - - - - - - - - -- - -- -

19i8 65 D l P 09:15 ebb 75 62 0 0 3 1 26 5 32 0,471 17 0

- 0 8.9 3.8 - 3 .8 -- 1.5 -- -. -

7 , r a q s e - i ~r ic! /st , s t !? . c' saivqple ( f t . be low

s u r c i c e i n b r a c k e t s )

iieigh c ( f r o i n y r a p t i ) ebb, f l o o d o r s l a c k

T o t a l o j s t f r l a r v a e p e r 103 1 i ti-t ,s ( f o r nits see n o t e a b o v e )

0 3 in;, J z - - L 1 C 1 q ^ ) C ; C ? I D r -

V-

Appendix I I . 1964

APPENDIX 111. Spa t coun t s f o r 1963 On s h e l l s changed d a i l y on r o u t i n e c o l l e c t o r s

n-..n~ , p x n . . ~ Spat --.. , "~ . . ... Soat t augit a LLGLR J I J I ~ L L L r e e K Dates i n Days ex- p e r s h e l l p e r s h e l l

i h t e r posed - 1' 4, 7 " p e r day 1' 4 ' 7 " p e r day ---

0 I1 1 0 .3 0 0 0 14 3 29 15 0 0 1 22 T68 386 86 4 13 42

0 8 52 20 0 2 35 0 11 102 3 8 0 3 15 5 2 0 294 106 1 24 86 2 12 175 63 3 5 2 192

1440 '38 4680 762 43 148 1032 0 1 6 2 .3 0 6 ., 0 1 8 2.7 6 9 42 1 4 33 11 2 18 28 0 5 52 2 1 4 3 57 0 0 5 0 .5 0 0 1

C o i i t ~ l ~ u e d moni tor ing tint11 22/8 1963, y i e lded only t h e fo l lowing s p a t . 1 0 3 1 0 0 2 0 I) 2 0 . 2 0 O 0

On \ h e l l s changed h ~ m o n t l ~ l y i n 190.7. 1 7 95 4 .9 1 7 8

126 1426 1531 7 3 11 320 663 132 1368 3752 125 2712

69 439 428 415 3432 102 409

140 3392 0 0 38 0.9

2 2 1 0 9 0 . 2 2 0 0

1 0 0 I 4 0 . 1

Molti torcd u i ~ t I l 70/9, btit no more spot s een .

AI'PENLIIX I V Oys t e r s p a t f a l l ; exposed d a i l y i n Smelt Creek, 1964

Mean o f Wean of- Date o f Spat on s c a l l o p s h e l l s a l l Spat on a s b e s t o s squa re s a l i Exposure Level 1 ' 4 ' 7 ' dep ths Level 1' 4 ' 7 ' dep ths

.July 28-29 J u l y 28-30 .July 29-30 . Iu ly 30-31 J t ~ l y 31 - / l u g . Ailg . -3-4 A u y . 5-6 Aug. 6-7 Aug. 7- 10 Aug. 10-11 h g . 11-12 Aug. 12-13 bug. 13-14 Aug. 14-17 Acg. 17-18 Aug. 18-19 Aug. 19-20 bug. 20-21 Aug. 21-24

To ta l f o r season

Oyster S p a t f a l l ; exposed d a i l y i n Paugh's Creek 1964

-- Mean o f

S p a t on s c a l l o p s h e l l s Spat on a s b e s t o s squa re s Mean of

Date of a l l a l l Exposure Level 1' 4 ' 7 ' dep ths Level 1' 4 ' 7 ' dep ths

J u l y 28-29 0 16 19 13.7 J u l j 28-30 3 1 1 2 5 13 J u l y 29-30 5 6 42 17.7 J u l y 30-31 0 6 32 12.7 I 4 1 2 J u l y 31/Aug.8 37 508 89 211.3 3 2 2 5 1 0 . 3 Aug. 3-4 0 2 3 1 . 7 0 0 0 0 Aug. 4-5 0 0 0 0 0 0 0 0 Aug. 5-6 0 4 3 2.3 0 0 0 0 A u ~ . 5-7 0 3 4 2 .3 0 0 1 .3 A u ~ . 7-10 2 7 3 4 0 0 0 0 Aug. 10-11 0 1 1 . 7 0 0 0 0 Aug. 11-12 0 0 0 0 0 0 0 0 A u ~ , 12-13 0 0 1 . 3 0 0 0 0 A u ~ . 15-14 0 0 0 0 0 0 0 0 A u ~ . 14-15 0 0 4 1 . 3 0 0 1 . 3 A u ~ . 17-18 0 0 1 . 3 0 0 0 0 Aug. 18-19 0 0 0 0 0 0 0 0 A u ~ . 19-20 0 0 0 0 0 0 0 0 Aug. 20-21 0 0 0 0 0 0 0 0 A u ~ . 21-24 0 0 0 0 0 0 0 0

T o t a l f o r s eason 44 55 3 202 268.3 7 1 7 53 26