ASPECTS OF THE LIFE HISTORY
OF TRESUS NUTTALLI IN ELKHORN SLOUGH
A Thesis Presented to the Graduate Faculty
of
California State University, Hayward
In Partial Fulfillment
of the Requirements for the Degree
Master of Arts in Biological Science
By
Patrick C. Clark \ \ January,l9Y3 ACKNOWLEDGEMENTS
The author would like to express his sincere appre ciation to the California Department of Fish and Game and the individuals who have been very helpful in assisting me towards the completion of this study:
1) To the California Department of Fish and Game
for funds provided for the research under con
tract number 6S-1401 for the period from
November 1, 1970 to October 31, 1971 and contract
number 6S-1414 for the period from November 1,
1971 to October 31, 1972.
2) To Dr. James Nybakken for his excell~nt guidance
throughout my graduate program and excellent
advice and support throughout this study.
3) To Drs. Mary Silver and Jack Tomlinson for their
membership on my graduate committee and their
helpful reviews of my thesis.
4) To Mrs. Signy Johnson for her help with the
histological work.
5) To Mr. Laurence Laurent for his tutorage at the
initial stages of this study.
6) Finally 1 to my wife, Joanne, for her support,
patience and understanding throughout my
graduate studies.
l TABLE OF CONTENTS
Page
LIST OF FIGURES $ • • • • • • • • • • • • • • • • • • iii
Section
I. INTRODUCTION 1
II. ~1ETHODS AND 1-'lATERIALS 3
III. RESULTS 15
IV. DISCUSSION • 21
LITERATURE CITED 26
APPENDIX A 27
APPENDIX B 34
ii LIST OF FIGURES
Figure Page
1 Map Showing Location of Study Area in
Elkhorn Slough • • • • • • • • • 0 4 2 Map Showing Five Sampling Areas . . . 5
3 Sections of Gonad Tissue; A: Inactive Phase; B: Early Active Phase ...... 7
4 Sections of Gonad Tissue; A: Late Active Phase; B: Ripe Phase ...... 8 5 Sections of Gonad Tissue; A: Partially Spawned Phase; B: Spent Phase .•.•• 9
6 Subtidal Rack for Growth Studies 12
7 Growth Curve for Tresus nuttalli from Elkhorn Slough, California . • • • • • • • • • • • 14
8 Gonad Condition of Gaper Clams Collected from Elkhorn Slough in 1970 • • • • • • • • • 16
9 Gonad Condition of Gaper Clams Collected from Elkhorn Slough in 1971 ...... 17 10 Gonad Condition of Gaper Clams Collected from Elkhorn Slough in 1972 ...... o \' e . 18 11 Total Number of Juveniles Between 2 to 4.9 mm Collected Each Month Per Square Meter . • 19
12 Average Monthly Temperatures for Study Area from October, 1970 to August, 1971 • 23
iii I. INTRODUCTION
In Elkhorn Slough the gaper clam, Tresus (=Schizo thaerus) nuttalli (Conrad, 1837) is an important sport species that is fished very heavily during periods of minus tides. Detailed knowledge of the reproductive cycle and growth rate of the gaper clam is essential for proper management of the gaper clam in Elkhorn Slough, California.
All studies concerning the reproductive cycle of the genus Tresus utilize Tresus capax (Gould, 1850). T. capax is a more northern species with the majority of its popu lations found above Humbolt Bay, California (Swan and
Finucane, 1952). However, there is a very small population ofT. capax in Elkhorn Slough (personal observation).
Winter spawning of T. capax has been suggested by Swan and
Finucane (1952) for the populations on the coast along the
San Juan Archipelago, by Reid (1969) for those on the coast of British Columbia, Canada and by Machell and De Martini
(1971) for the population in Humbolt Bay, California.
Tresus nuttalli has been reported with shell lengths as great as 250 mm in length and this species is considered by Nicol (1964) as the largest recent American clam. As yet nothing has been published concerning the growth rate of
1 2 either T. nuttalli or T. capax~
MacGinite, in a 1935 study, warned that the heavy clamming pressure endured by the many species of game clams in Elkhorn Slough might lead to the local extinction of these game species. Three of the bivalve species that
MacGinite counted as common or abundant (Protothaca staminea,
Saxidomus nuttalli and Clinocardium nuttalli) can now be counted as few or rare (personal observation). It is the purpose of the present study to determine the reproductive cycle and growth rate of Tresus nuttalli so that these data might aid the California Department of Fish and Game in the proper management of T. nuttalli in Elkhorn Slough. Thereby - I hoping to spare the gaper clam in Elkhorn Slough from the same fate that befell the other game clams of that alough's mudflats. II. METHODS AND MATERIALS
Spawning Cycle Study
A minimum of ten and.a maximum of twenty-four Tresus nuttalli above 90 mm in length (greatest posterior-anterior dimension) were collected during each series of daylight tides lower than -0.7 feet from a mudflat in Elkhorn Slough
(Figs. 1 & 2). Collecting was done by shovel with the sites of collection determined by random selection of areas within each of the five sampling sites (Fig. 2). The clams were brought into the laboratory, where their lengths and widths (greatest lateral dimension) were taken to the nearest millimeter with vernier calipers. The soft parts were preserved in 10% buffered formalin. Gonadal blocks were dissected from the dorsa-posterior area of the fixed body, dehydrated and infiltrated by the dioxane-paraffin method of Galigher and Kozloff (1964), embedded in paraffin, sectioned at seven micron intervals and stained with standard hematoxylin and eosin procedures (hurnason, 1967).
Upon examination of the gonadal preparations, each individual adult female sampled was placed into one of five developmental categories established by Ropes and Stickney
(1965) in their study of Mya arenaria: 1) inactive;
2) active; 3) ripe; 4) partially spawned; and 5) spent.
3 I I
Aptos
''I / I ( I » I I 0 I I I 3: I I I .c l 1 I 0'1 I I I I \ ::c I ( \ \.1 l \ (/) \ \ ,study \ ::J N I \Area \ \ ',~Fig. 2)\ "- \ I '" 1 -36 ° 50
» 0 ill » (J),__ (J) 121° 50 1 -c: 0 L.
f--j ~ .I n.mi. n. mi.
Moss ~ .... Pocitlc Landing Grove '}! !Marine /CJ !Laboratories (B) Fig u r e I A . M ~ p shows location of Elkhorn Slough in center of Monterey Bay. Are;a within the square is enlarged in Figure 18 To shew .c:;1udy area. I 5 ( H I
r (
f
------~ ------.., Are a I \ ------
Area ~ -I 2 ~..... _ f tn1 ------I ~- I' l Are a I Are a Are a I 4 5 ) 3 I I I r I l, I I ___..,.- I I I CJ I I
Fi g u r e 2 . S t u d y a r e a s h o w i n g f i v e s a m p I i n g a r e a s .
100 feet
~------~------~ 6
The inactive phase was characterized by collapsed follicles with few to no oognia present (Fig. 3A). In the early active phase the follicle wall began to thicken with the follicle cells beginning to form oogonia (Fig. 3B). In the late active phase the alveolar wall was thin, the oogonia elongate, at which time th~y were considered primary oocytes, and the oocytes were attached to the alveolar wall by means of stalks (Fig. 4A). When there were more oocytes laying freely within the lume~ than were attached to the alveolar wall, the ovary was considered to be in the ripe phase of development (Fig. 48). In the partially spawned phase the alveoli were partially empty and the follicle wall was slightly thickened (Fig. SA). The spent phase was characterized by inflated follicles with degenerating residual oocytes and debris (Fig. SB).
Since it is impossible to distinguish inactive females from inactive males, the number of specimens in the inact state were divided in half and the resulting quotient was used as the number of inactive clams. Laurent (1971) found that within his samples the ratio of males to females was 1:1 (P=.95, Chi square tes·t). This ratio was assumed to exist in the samples obtained for this study.
The population density of juveniles (clams less than
75 mm in length) was measured during each series of dayl tides lower than -0.7 feet in the five sites of the mudflat f 1
7
A.
B
Figure 3. Sections of Gonad Tissue of Female Tresus nuttalli; A: Inactive Phase (4X); B: Early Active Phase of Oogenesis (lOX). 8
A
B
Figure 4. Sections of Gonad Tissue of Female Tresus nuttalli; A: Late Active Phase (4X); B: Ripe Phase of Oogenesis ( 4X ) . _____. 9
A
B
Figur e 50 Section of Go nad Tissue of Female Tr esus nuttalli; A: Part ially Spawned Phase (4X); B: Spent Phase o f Oogenesis (l OX ). 10 sampled for adults. Densities were determined to test for correlations between the number of juveniles settling and
-the gonadal condition of the nature population. From each 2 of the five sites a sample of 0.15 M was taken and exca- vated to a depth of 12 em. The substrate within the samples was.sieved through a 2 mm mesh sieve. The residue was then taken to the laboratory where all the live Tresus were removed, measured with vernier calipers to the nearest 0.1 mm and a frequency distribution and histogram constructed.
Growth Rate Study
There are two possible methods of determining growth in bivalves: 1) by following a size class through time; or
2) by repetitive measurements of a marked population.
Laurent (1971) attempted the former method and was not successful in estimating growth; nearly continuous recruitment prevented the following of one size class through time. The latter method was started by Laurent and myself in February, 1971 on an experimental basis.
Originally, we took juveniles collected from the juvenile population study, measured them to the nearest
0.1 mm and planted them in two plastic buckets located subtidally in Elkhorn Slough. We retrieved the buckets fifty days later on March 2,, 1971. Since we had not mark0 the juveniles, we were unable to determine anything but a mean growth in each bucKet. These juveniles were marked 11 with printed numbers attached to the right valve and the numbers were covered with Dekaphane. The buckets with their marked juveniles were returned to their racks on
March 25, 1971. They were then retrieved May 18, June 12,
September 15 and November 3, 1971. Three more plastic containers were placed subtidally in the slough on June 14,
1971 to make a total of five containers with marked, premeasured juveniles. When the containers were retrieved, the clams were remeasured and those that had died were replaced with freshly collected juveniles. The containers were returned to their subtidal racks. Sometime in
December, 1971, all of the containers were overturned and the contents lost. In March, 1972 two racks of much sturdie construction were placed in the slough (Fig. 6).
The new subtidal growth racks utilized four, six foot
long fence anchors buried into the slough bottom approxi mately two feet. To these fence anchors were attached two
3• X 4 1 sheets of plywood which were sealed with finishing
resin. The uppermost sheet of plywood contained fifteen,
five inch diameter holes through which were placed four
inch diameter PVC (polyvinyl chloride) pipes three feet in
length. One end of each PVC pipe was sealed by means of a
sheet of rubber and a hose clamp. The pipes were filled with sediment which was obtained either from beach sand
that had been sieved to remove most of the organic debris
or from the slough bottom. At least one gaper clam was 1;
PVC tubing~
,,I ,, 'I 1 -- 1--.. II ',, ~,'\~ 11'"n------'...... ,':_, 11 , .:rr--~~ II -, ,, I' ' ,, \ u
Figure 6. Subtidal rack for growth studies 0 f nutto!lj. 13 placed in each pipe, and the juveniles were placed in smaller diameter PVC pipes that then were placed within the larger pipe.
Each clam was removed from the rack at intervals depending on the clam's size: 1) those less than 10 mm were measured at one ~eek intervals; 2) those between
10 mm and 50 mm were measured at one month intervals; and
3) those greater than 50 mm were measured at three month intervals. A graph of length versus time in days was con structed for each clam. This line was then resolved into points with each point representing one day along the growth line. Size classes were then chosen with the class interval being 5.0 mm in length. All the points that fell within each size class were combined. A regression analysis was conducted on the points within each size class to obtain a line for each size class. These lines were then connected end to end in a progressive order of size starting from the smallest measured individual and progressing to the largest measured individual and progressing to the largest measured individual. From this procedure a non-smooth growth curve was obtained. The curve was then analyzed by means of a curvilinear regression analysis to obtain a smooth curve
(Fig. 7). All the computations were done on a Wang 700
Series Advanced Programming Calculator (See Appendix A). 60 ------=- --
50 / / / ./ / ./ / / _, ... 40 / / / / / / ..--- / / :::::::=Approximate 95% prediction band E / / E / 30 / "' / ..c. / / ..... / 0> / c / / Q) / __J / / / 20 / / / / / / / / / / / 10 / / , / / / / / I / I 0 t'; 0 50 100 150 200 250 300 350 400 450 500 550 Age (days) Figure 7. Growth curve for Tresus nuttalil from Elkhorn Slough, California.
li III. RESULTS
Spawning Cycle Study
Gonadal sections of adult Tresus nuttalli have been studied from specimens collected during the period from
February, 1970 to June, l972o Measurements on those speci mens obtained between February, 1970 and December, 1970 were data obtained from Laurent, 1971. Only females were considered in this study. Males were not considered due to the difficulty of determining their state of gonadal development. Samples were not taken during the months of
September, 1970 and September and October, 1971 because there were no tides below -0.7 feet during daylight hours.
Juveniles and adults were collected during the months of
February and March, 1972 for the growth rate study. Since these specimens were to be kept alive no spawning cycle data were obtained.
Figure 8, 9 and 10 indicate the gonadal condition of female clams sampled between February, 1970 and June, 1972.
The data on the density of juveniles suggests that settling occurred during every month in the sampling period from April, 1971 to June, 1972. Very definite peaks were noted during May, 1971 and April, 1972 (Fig. 11 and
Appendix B).
15 N: 12 2 13 5 4 3 7 5 4 4 100
90 l 1 80 j 70
60 ,._ c Cll (.) 50 I... 30 20' Jan March Apr II May July Sept Oct Nov Dec 1970 Month Figure 8. Gondd condition of female gaper clams collected from Elkhorn Slough. The length of each shaded area represents the percentage of clams in each gonadal condition. N= number of ~::males sampled. N 6 4 4 5 8 7 5 4 8 100 90 80 70 60 -c 50 30 -t - ,, 20 10 Jon r-eb April May June Juiy Aug Sept Oct Nov Dec 1971 Month Figure 9. Go nod condition vi female gc~,(: r clams co lie c ted from Elkhorn Slough. The length of each shaded area represents the percento ge of clams in each gonad a I condition. N = number of females sampled . r-> N: 14 15 10 14 100 90 80 70 60 +- c 50 30 20 10 Jan Feb March Apri I May June 1972 Month Figure 10. Gonad condit:(\n of female gaper clams collected from Elkhorn Slough. The length of each shaded area represents the percentage of clams in each gonadal condition. N= number of females sampled. Leqend for gono d condition ~ inactive, ffEEfHB active, /======:1 ripe, ~ partially ,...... co 200 \ !50 ..... (j) a. .... (!) ...0 100 E z::J 50 0 April May June July Aug Sept Oct Nov Dec Jan Feb March Apri I May June 1971 1972 Month Figure II. Total number of juveniles between 2 to 4.9 mm collected each month per square meter. 20 Growth Rate Study The gaper clams placed in the subtidal growth racks ranged in size from 2.2 mm to 143 mm in length. A growth curve was compiled for those clams between 2.2 mm and 55 mm in length. When this curve was smoothed by means of a curvilinear regression analysis, it fit the equation: Length (mm) = .0027 + .2043 (age in days) -.0002 (age in 2 days) , (Standard Error= .41) (Fig. 7). Those clams greater than 55 mm in length were not in the subtidal racks long enough to provide enough data to extend the curve. It is apparent from this study that adult gaper clams, above 75 mm in length, should remain 1n racks similar in size to the ones used in this study for at least a year to obtain a complete growth curve. IV. DISCUSSION The gonad sections for the period from February, 1970 to June, 1972 indicate that the primary spawning period for gaper clams in Elkhorn Slough is from February through April. This is inferred from the high fraction of females that are ripe at this time. The juvenile density study indicates high numbers of newly settled gaper clams (2 to 4.9 mm classes) per square meter during May, 1971 and April, 1972. There appears to be approximately a one month lag between spawning as determined from the gonad sections and the appearance of a high peak of newly settled juveniles in the samples. For example, fifty percent of the adult females sampled in April, 1971 were in a ripe condition and all the females sampled in May, 1971 were in an active condition (Fig. 9). This change in gonadal condition indi cates that spawning occurred between the two sampling dates. The juvenile density data indicate that there was a peak in juvenile settling in May, 1971 and a decline in June, 1971 (Fig. 11). The point of intersection of the abscissa and ordinate of the growth curve (Fig. 7) is that point where the velige begins forming a calcium carbonate shell and settles. Sine the actual data begins at 2.2 mm in length, the growth curv 21 22 was extrapolated back to zero using the growth equationo This procedure indicates that it takes approximately ten days from settling in order to grow to a size of 2 mm and twenty-five days in order to grow to a size of 5 mm. Loosanoff (1963) states that most temperate bivalves have a maximum larval life of thirty days. If this is true for the gaper clam in Elkhorn Slough, then spawning would have occurred from forty to fifty-five days prior to the observed peaks. Judging from the dates at which the two above mentioned samples were collected, I would predict a larval life of twenty-one to thirty days for the gaper clam in Elkhorn Slough. The work done by Machell and De Martini (1971) on Tresus capax in South Humbolt Bay, closely parallels the spawning cycle study presently being reported. We both determined that winter is the primary spawning period: Machell and De Martini determined that spawning occurred from January to April; I determined that spawning·occurred primarily from February to April. Machell and De Martini determined that the active phase was associated with the highest temperature and salinity measurements in their study area and spawning with the seasonal low values for temperature and salinity. I determined that the active phase was associated with the initial lowering of the water temperature at the study area and spawning with the sea sonal low values for temperature (Figs. 8, 9 & 12). 19.0 18.0 17.0 16.0 (.) 0 --" 15.0 ro.... ::J 14.0 0,_ Q) a. 13.0 E Q) 1- 12.0 11.0 10.0 9.0 18 16 19 28 27 27 24 22 23 ., 22 16 Oct Nov Dec Jan Feb March April May June July Aug Figure 12. Temperature for I meter depth at Sea Grant Station 8 1 30 yards off sampl-e area. Temperc:tures were token at highest high tide on days indicated. Hourly temperatures 2,4. __ \--:"-_c:."'-u- ~~..-1 ..:3ds .c.':lor>. 2"7 Feb ... c::.r-,d iS Aua \.Vith The ranaes olo1'fed (Srnlfh_ }972_ ."? 24 Machell and De Martini found spat only during the spring, whereas I found spat throughout the whole year. The reasons for the observed differences are probably many. The primary reason being that Machell and De Martini and I are dealing with different species. One possible c~ue as to the differences in spat settling times could be the large ranges of water temperatures found each day in Elkhorn Slough. For example, on February 27, 1971 the water temperature varied over a twenty-four hour period from 9.6°c to l3.4°C and during August 16, 1971 it varied from l3.2°C to 19.2 0 c. The temperature range for August 16 is noteworth) since it falls within the range of daily water temperatures recorded during the spawning season and yet it is not in the spawning season. Perhaps, the wide daily fluctuations ln water temperature in Elkhorn Slough explains the presence of ripe females and newly settled spat in the population throughout the year: temperatures sufficiently low enough to trigger spawning may occur during a number of ·seasons in Elkhorn Slough. If the daily temperature ranges in Hurnbolt Bay are smaller, the difference in spawning behavior between the two Tresus populations might be explained. The growth curve (Fig. 7) can be used to estimate the length for a clam of a given age. For example, a gaper claf.r one year old will be within 49.45 to 50.27 mm in length 95% of the time if it is found within Elkhorn Slough. Gonadal sections demonstrated that female gaper clams above 70 mm in Elkhorn Slough have ova that appear mature. The growth curve indicates that the age of maturity for a female gaper clam or the age of a 70 mm individual is at least two years. The method used here to determine the growth rate of the gaper clam in Elkhorn Slough has never been reported in the literature. Until now there were two options for determining a growth curve: l) a model for growth was used i.e. the standard exponential curve; or 2) a number of spec mens were observed from birth to death. With the method described ln this paper it is possible to obtain an accur~ growth curve for an average individual of a population ln two years. The only requirement being that the animal add length, width or height with age. The present study also provides some data on year to year fluctuations in recruitment. The population density study (Fig. 11) indicates that the recruitment during 1972 was more than twice as great as the recruitment during 19~ If there are no catastrophic occurrences on the mudflats ~ Elkhorn Slough, 1975 should be a good year for harvesting gaper clams! LITERATURE CITED Galigher, A. and E~N. Kozloff 1964. Essentials of Practical Microtechnique. Lea and Febiger, Philadelphia. 484 pp. Humason, Gretchen 1967. Animal Tissue Techni~. W.H. Freeman and Co., San Francisco. 569 pp. Laurent, Laurence L. 1971. The spawning cycle and juvenile growth rate of the gaper clam, Tresus nuttalli, of Elkhorn Slough, California. Master's Thesis, San Francisco State University. 55 pp. Loosanoff, Victor L. and Harry c. Davis 1963. Rearing of bivalve molluscs, p. l-136. In Advances in Marine Biology (Vol. 1). Academic Press, London and New York. 410 pp. MacGinite, George E. 1935. Ecological aspects of a California marine estuary. Amer. Midland Naturalist Naturalist 16(5): 629-765. Machell, John R. and John D. De Martini 1971. Ann annual reproductive cycle of the gaper clam, Tresus capax (Gould), in south Humbolt Bay, California. Calif. Fish and Game 57(4): 274-282. Nicol, David 1964. An essay on the size of marine pelecy pods. J. of Paleontol. 38(1): 968-974. Reid, Robert G. B. 1969. Seasonal observations on.diet, and stored glycogen and lipids in the horse clam, Tresus capax (Gould, 1850). Veliger 11(4): 378-381. Ropes, John W. and Alsen P. Stickney 1965. Reproductive cycle of Mya arenaria in New England. Biol. Bul. 128(2): 315-327. Swan, Emery Frederick and John H. Finucane 1952. Obser vations on the genus Schizothaerus. Nautilus 66(1): 19-26. 26 APPENDIX A Growth Rate Program to be used on Wang 700 Advanced Programming Calculator 27 28 GROWTH RATE PROGRAM 1) Insert Tape, Key: REWIND, TAPE READY, PRIME, LOAD PROGRAM 2) VERIFY PROGRAM 3393 should appear in the X register. PRIME TO PRINT OUT HEADING 3) SEARCH 0 Prints out heading GROWTH DATA 4) Key number of lines to be resolved into points (N) 1 GO 5) Key end point of line (Yx), GO 6) Key origin of line (Y ), GO 0 7) Key slope of line (b), GO 8) Results will be printed out; when print out is complete return to step 5 and enter data for the next line. Repeat steps 5 thru 8 until all data is entered. TO PRINT OUT RESULTS 9) Key GO X - mean of X Y - mean of Y b - slope of resulting line Sb- standard deviation of the slope n - number of points 29 EXAMPLE: GROWTH RATE PROGRAM - . Line fl:l Line #2 Line #3 N . - ~ y 2. 76 mm y = 2. 78 mm y = 2.69 mm X X X y = 2.2 mm y = 2.2 mm y = 2.2 mm 0 0 0 b .14 b ·- .13 b .14 GROWTH RATE ORGANISM: CLASS: X y 2.200 1 2.340 2 2.480 3 2.620 2.200 1 2.330 2 2.460 3 2.590 4 2. 720 . 2 0 200 1 2.340 2 2.480 3 2.620 x = 1.692 y = 2.429 b = .1337 Sb = .1881 n = 13 700 PROGRAM TITLE: NO. JO Step Code Key Comment Step CGde Key Comment 0">0 on rF REG 05 OSl {')!, ()!, S'T' DTR 052 oo or, RE~ 06 053 {)!, 01, ··~nTR· O'il 00 07 'RlU! 0'7 nr:r: fll (){ ~I'J1 nTO 006 Ql, 0')(, on o:1 RR~ OR 007 ()l, 057 Q4 oz. ST DIR On'· 15 U:>H w.u Fl REG 10 00? () .'~ OSQ 0/f 0/1 ST DIR 010 15 (}()() ()[) ll REG 11 011 0/1 12' Uhl {)lf ()If ST· DIR 00 15 G or,z 'DO 12 REG 12 01 13 R ()fd 'IJcf (JI< ·ST DIR 0(Jlf '(D') lJ 01 '·9' 0 REG 11 r~ ,:-.o-·- w 0(,5 Ol! Qh ST DIR 016 _1_:! 117 1 T Oli6 00 llf REG 1-4 017 02 01 H 0(17 Ql, Qt, ST DIR 018 00 01 2 SPACES OG:l 00 15 REG 1 c; 019 01 13 0(,'1 05 15 STOP KF.Y N 070 (}4 ot, ST DIR 071 00 10 REG 10 072 Ql •Ofl' ]1;,1\RK 073 f)7 OJ. 1 07/1 >7 on 0 07" nt nt ST DIR 07G on on REG 00 077 :0& 01 ST DIR 01 12 07fl no 01 RF.,_G__Ql 02 on N 079 l}t. Q/, ST DIR 030 01 Gt. I 080 00 02 REG 02 031 ----01 Ol s 081 .04 01,' ST DIR 032 01 1 c,l M 1182 00 01 REG 01 031 _Q.!]_J) ,_J)11 04 01 ST DIR 034 l)fl/f ..00 '0'1 REG oq 035 01 10' LF'' OflS O'i 1 'i STOP 'KEYY'X 036 02 12 Of1G 0/ 0! ST D_IR r--037 02 09 Ofl7 nn nn REG 00 ~_933 QL;'2 0:18 f)'i 1'i. STOP KF.Y Y.o__ ; 039 flWl Ql, n.t, ST DB WlO I on m • REG 01 nrn [ J).t:; lt:; ·~-p KEY b 0<)'> '!'II ()[, S'T' DTR 093 on 02 REG 02 094 Q!; or. MARK t 0'15 ! f)7 02 2 lo'lh · r~. '0;! R.., THR I · 097 4=fr1 rn RF.r, _QJ_ 11'1R- 04 'I WRITE --~RITE X J.O - oqq J.::Q.LOo - - Remarks: 700 PROGRAM TITLE: NO. 31-·· Step Code Key Comment Step Code Key Comment 100 Ol1 ll WRITE l"() ()I ()() . + DIR 101 1:i 02 2 SPACES FJ 01) 11 REG 11 102 Q(j ()tl 1 L'i::! f)/1 0.". RE DIR 103 011 no + DIR 'r, 1 on Fl REG 10 104 00 01, RF.!1 04 2X 1 r: I nr. nt TO'\ nr or; RE nTR l'i'i ()/, ()t; RF. "' DTR f--lDJL 00 07. REG 0? 1 r;£; on 11 RF.!1 11 ~07 or, 02 X 1 'i7 or, ()(, H - _llli.1 . 0-'t.J.!.S.f-~~DTR 1 r: :l ()t; ()'1 SKIP -~-f Y X 109 0•1 01 REG 01 1"<1 ()/. (17 SEARCH 110 (j(, 0!1 + 1(,() 07 01 1 111 () lj__j;_~i '1- 1(.1 ()l, 05 RE.DIR y 112 O!.'~_j l ':/RITE WRITE 1112 Of) Ol: REG 04 113 0) ':J ---~ I-J}i1 ' 07 1.1 x--z 114 ()(, 1 / ~':~ITE ALPH lf,l, f)(i 0/f I ot. or; · F.~ "' f-•liS. <- ____a ].__(hi f-·CR.J.':LF lfi5 D::p_ 116 Ol ll END ALPHA 11)(, on 12 RGG 12 117 04 Ol ST DIR y 1(, 7 or, ()) , 1 [! no oCJ REG 09 1Gfi Ol, f~\) RE DIR 119 Ql, 00 + DIR 111'1 ()() ";(j REG 06 120 00 l)'j REG OS 170 or, or, H J'?l ·.07 1\ x:c: 171. nG m - - 1'1? .04 nr' + DTR z. yc. 17'' .')(; (J 'i t 1?'\ nn n RR!1 07 171 01 (){ C:rJ1 DTP. :i=d Step Code Key Comment Step Code Key Comment 200 no l'i RE_G_l_c;.L---t-~------1 2'i0 1 'i O'i '5 SPACES 20] nt~ 05 RE DIR X 7.'i1 01 p WRITE ALPH 202 ''l fl.', REr;--->e024_-+------I 2S2 rn 02 SHIFT DOWN I 201 0 'j 1 :, ~IT.£..._p---+--:c::=--:=::-'!:':!'------1 zr 1 _D7 on b _204 0!; 1 I WR T'T'F. WRITE X 20'i 1 'i 'F _') SPAC~S ?.Ori Ot 1:2 WRITE ALP'--'-)H-'-"+------1 2'irl on 02 SPACE 207 01 01 SHIFT UP 20° on no ----+------1 209 ()!1 ~ 1 END ALPHA 210 Ot1 11 ':IR ITE 260 0!1 05 RE DIR 211 15 1~ 1 ::;-~PACES ·------1 2ril oo 15 REn 1 r:; 212 04 12 WR. -::-'-'l=-''~E~A-==L"-"P-"-H,_,_:Pl------1 2F.7. 0!1 05 RE DIR ~XY 213 oo r,? SPACE 26 -;·-+--"-00"----'-'-0--'-il +-....,RE~"~0"'"'1 8""-----+----- 2ll -on no 2f>ci 07 lJ X .C . 21 ; n i r'J.l.:l+--c=R-j"-;_,'-F--_--t------1 2lt 0/ 11 END ALPH_~·---+------1 ,_ _2_!_" _Q4 11 WiUTE I ?' ,- lS_O'i S SPACES Gl9 04 ~' WRITE ALPHA 2fiCJ 04 O.'i RE DIR ~ y-.c t?zn 01 rn SH IYl' UP ~21 02 , ~ X i "77 nn 0" SPACE 177.. Ofi 01 1 ; _n. .l n? SHIFT DOWN 7.71 O!i O'i t n:J n,; = 27.!6 04 13 END ALPHA 27!i Ot. O'i RE DIR •.. 2'27 Ot• 11· WRITE 277 Oil P REG 12 n ~ ??B n__ ·_ 01 2. 1 1 r~?'7~·:~~-~n,r-Jn~.r~ __1 ____ ~------229 04 >l5 RE DIR 2 230 00 ns REG 0 5 y 280 nr, 01 2 31 Ol1 11 'I;R i ~':2.: 2fll 04 05 RE DIR 232 15 06 f-. SPACES 2fl7. 00 ltl_ REG 14 231 Ot1 T' '#FUTE ALE}ti------1 234 01 03 SHIFT U.t- -+------t 235 00 01 y 236 _:'o n2 SPACE ~37 __ Jl 02 SHIFI' DOiiN 238 no or, = _ 1 ----- 2 YJ ' oo n2 s 'A : ~ -2411 Ot 1J END ..~.:.:,""p=~i"'"-A~+------· 'W Ot S'T' DTR ~-=-'--+------nt 2[,1 nt 11 WRITE J_cn no on R"' ~ o o "~4? ~01 ),) 7.CJ? 01 O'i R"' DTR ?l11 Ql' 12 WRITE ..!.!\L"-'?'-'-H~A-'f------1 244 01 Oil GR/LF 245 01 10 INDEX (LF ? M, nL. 1 1 E ND::..:=A=::JJc:p_c:-H"-'A::.::.....'+------l 247 nt. ns RE DIR b ·ng nn 1 c; REG 1 ') ?t.Q nt. 11 WRITE Remarks: 700 PROGRAM TITLE: NO. 33 Step Code Key Comment Step Code Key Comment -~ II" or b --~.21._-~.1~ o~. SPACE f... 07- · I f.ll -==~-=-----1------J _ QJ_I-- l n~ _=S==-Po,-h:..:: .. C:::cE"'-=:-::-:---+------l 1-----Qt · .iL..L_ ~ND_l,LPHA r-:~J s 11 1 L_l'V.,_,_P'-''I"-"T,_,E,___-+------1 3Dli 01 nt. 1.4 307 04 12 WRITE ALP'_-~r----·- 10.'1 m _0," CR/LF 1----t ------jl------+------1 J~_r, OJ. 10 INDEX ( LF _1.!'/ ____QtL 11 END ALPHA .. _3_~ L r--f._Lcs.~E'----=-"D~I"--'=R'---+--..u....n ___-t ,_ __ll~ 00 -. 2 _p:-:--::Gc-.::c-=:1:-=2=-----+------i ~_]lJ__ (){, 1 II w . I'::'E -::-- _ _.:._ ____--+ !------+--+-----+---==--·__ =:] t -~·-c· ~PACES ------1-----t------+------1I wr._,_____Q_{~ Wr ~1_-:; r,_L.P'----'H,_,_ .•'-'1:.· ______-l . ~lfi 01 o•, Sl-=I=-Fr-=--=D--=-O_c:__\'1-'-l\--+------l 317 07 or, n :118 no _0:' SPACE ~~·19 oo or) = r-:, 70 nt- o ~,i=-'S:7P;,-:A,__,_v:;--;E='=,~-i------l I 3?1 Ot 1- EN~D~A~L~P_,_H~A'--+------1 1-----1----+------+------1 "'J? ot. 11 WRITE ;;-· ot _1 END ALPHA l·--·-·------1 f-----i--~i,______-+------1 1u7 os 1 lEND FROG I _j -=__l·-======::±::::±======::!:::===-::::d Remarks: APPENDIX B Frequency Distributions of Juvenile Clams Collected Between May 12, 1971 and June 12, 1972 34 10 n I I ::>-. u c:: I I 0:0 I ::J u .-- (l) .,_..... 5 0 I..__J--t----\---11---1-----+-+1~-~~-~l [l-+-D-I--.-...---+-[h..J-.-J.-~D:n----J---+-----~---r--.---r-='-=-""' ..---.---1-----~0 I 5 10 15 20 25 3 0 Size Cia ss {m m) (A) 10 ,..., u c:: Q) ::J u Q)...... 5 0 1--i--+--lm-l-+---.-----.---·..----.--.+--D---~·-"---r---T·---r---r---,----,.----r•----.--tO--t----r--..- 5 10 15 20 25 Size Class (mm) (8) Frea.uenc'l distributions of juvenile clams collected on April 26, 27 8 28, 197/ (A) and 40 ~ 35 30 25 ---.-' 15 10 0 n. n n n _CJ 5 10 15 20 25 Size Class tmm) Frequency distribu don uf juvenile ciams coll::;cted on May 26 a 27, t97l. c: 0 0 u E Ul s E Ul 0 Ul 0 u u m c: C) > ::J c: 0 >. u c: Q) :J cr (!) ,_ 0 LL L() ~ 10 1 I) c mI I --: ~~J ~ .;:: 5 o, 5 10 . 15 20 25 30. 35 Size Class tm m) (A) 10 >- 0 c (!.) ;:J 0" Q) ..,_..'"-- 5 0 -, I. I I.' I D-D 5 10 15 20 25 30 35 Size Cluss (rnm) (B) Frequency distributions of juvenile clams collected on June 23 1 1971 (A) and July 9 B 10, 1971 {8). w = .3 l{) r0 1'- (j) 0 r0 r0 N :>. :::l J c I_() 0 N -o (I) -(.) E ':J _Q '- r -(/) l -o >. l r (.) c (I) :::l 0" d (I),_ LL. 1.{) 0 l{) 0 1\ouenbaJJ. 4o c: 0 I[) u C\J CD (_) !l) 0 (_) 0 "0 c 0 1'- O'l :=J ..0 '- I[) >. {[) (_) c .... (],) (f) :J ~ 0" 01 Q) ~ Ll... <( 0 1.() 0 ,l;::>uanbaJJ. 5 , ;,., I '·'r: "'::J i.7 ,_,J.) j l _-.-Q L-~+-~~-+-4--r-T-~r-.--r-~~~-r~~--r-Tr~--.-.d I I I 5 10 15 20 25 Size Class (mm) (A) .-- :;..-. u r-- c 5 1 il) ::J cr 1-- r-- Q.._ 4-· 0 L n o-J D 5 10 15 20 25 Size Class (mm) ( B) Frequency distr'1butions of juvenile clams collected on January 15, 1972 (A) and January . 27, 1972 (B). n 20 15 - -'-- .-- 5 1: I ..--- m 0 ~ .. ]J 5 10 15 20 25 Size Closs (mm) Frequency distribulion of juvenile cldms collected on November 3 8 4, 1971. r J ,~ >. u c 15 10 I 5 :-- I I I ~ ,- ····---- I -·- [TI I I I 0 +-l n n ' . 5 10 i:J '"0 25 Size Class (mm) ( 8 ) clams llccted on December I. 1971 (A) and 45 ...-- .. 44 40 1--. 35 .--- 30 25 '+- 20 15 ,. 10 I-- I-- 5 1---- r-- 0 n n II 5 10 15 20 Size Class (m m) F r e q u e n c y d i.s t r i b u t i o n of juvenile clams collected on April 16, 20 - ,.-- r-- r-- r- 1-- 15 I--- ~ r-- .--- }-- r- •'. 5 f- ,-- .-- r-- 0 n n 5 10 !5 20 25 30 Size Class (rnm) Frequency distribution of juvenile clams collected on May 15 1 1972.