THE ECOLOGY OF CHIONE CANCELLATA1

HILARY B. MOORE AND NELIA N. LOPEZ Institute of Marine Sciences, University of Miami

ABSTRACT Chione cancellata occurs intertidaIly and sublittorally. It is mature at a length of about fifteen millimeters and an age of one year. There is little growth after four years. Chione spawns twice a year, in the winter and summer. Shell growth is positively correlated with temperature in im- matures, but is depressed in summer in adults. The annual productivity is about 83 per cent of the standing crop, and half the productivity is in the form of spawn. A rich intertidal community produces a dry weight of tissue of 7.9 gm per square meter per year. An account of habitat and behavior is given.

INTRODUCTION The family Veneridae, including the genus Chione, is of worldwide dis- tribution, and its species are important constituents of various bottom communities. The species Chione cancellata Linne ranges from Cape Hat- teras to Brazil, including Bermuda and the West Indies (Abbott, 1954; Dall, 1903). In view of its importance, it is unfortunate that almost noth- ing is known of its ecology. A long-term study is in progress on the communities in Biscayne Bay, Florida. This is considered to be a typical tropical shallow-water estuary; basic information is needed on the ecology of such an area, and particularly on its productivity. In a study of the infaunal communities in the soft bot- tom in this area (McNulty et al., 1962), C. cancellata was found in all but the coarsest sediments. The following mean numbers of animals per square meter were found at the corresponding median diameter of sedi- mental particles: 0.31 « 0.2 mm), 0.36 (0.2-0.4 mm), 0.83 (0.4-0.6 mm), 0.0 (> 0.6 mm). At an intertidal station referred to later, a density as high as 162 per square meter was recorded. We are indebted to the Department of Health, Education and Welfare for supporting this study (grant No. WP-00573). Several graduate students studied this species in a course on marine ecology, and their reports have proved of great value. We wish to thank R. L. Aaron, C. N. D'Asaro, G. Reyes and A. D. Mathias for allowing us to use their data. We are also grateful for help from many other members of the laboratory.

MATERIAL AND METHODS The community survey led to detailed quarterly sampling of two selected areas in 1957 and 1958. This used a one-tenth-square-meter Van Veen

1 Contribution No. 987 from the Institute of Marine Sciences, University of Miami. 132 Bulletin of Marine Science [19(1) grab. Numbers per square meter were estimated, as well as size frequency. A single series of tissue-weight determinations was made, and from these the seasonal variation in tissue weight per square meter was estimated. In the present study it was considered more desirable to obtain large quantities of material than to know precisely from what area of bottom it was taken. We therefore used a mud bucket for collecting. An approximate calibra- tion of the bucket (Moore & Lopez, 1966) gave a value of 6.24 buckets per square meter of surface, so the results of this series are roughly quan- titative. In the summer of 1965, a series of transects were made down the intertidal zone on the Seaquarium flats, close to the laboratory (Moore, et al., 1968). These have provided a good estimate of the general abund- ance of Chione in such a habitat. Finally, sampling on a selected inter- tidal location of these flats was commenced in July, 1964, and repeated at frequent intervals up to July, 1966. It is the work at this location which has produced most of the following data. This location is shown as station F on transect 1 in Figure 2 of Moore et al. (1968). This is slightly below mean low water of equinoctial spring tides. At approximately monthly intervals, a sample of about two hundred Chione from this station was brought to the laboratory where the size fre- quency was recorded. About thirty animals covering the full size range were then opened. The length and width of the gonad of each were mea- sured, and a small fragment of the gonad removed to make a smear prepa- ration. The sex of this was recorded, together with the degree of ripeness of the gonad. Finally the tissues were removed from the shell, dried for 72 hours at 105 °e, and weighed. The gonads were found to mature at a shell length of about 16 mm. For the animals above this size in each sample, the regression of dry tissue weight on the cube of gonad length length + breadth) 3 and on ( 2 were determined. The regression of weight on shell length cubed was also determined. Tagging was performed with very small, numbered plastic tags cemented to the shells with "Plasspar," an epoxy resin which has the advantage of adhering to a wet surface. Tagged animals were released both free on the shore and in pens, but losses occurred sporadically because of storms, in- terference, and other reasons. We ended up with data for about a hundred free animals. In addition we have growth data for about 350 tagged in- dividuals kept in a tank in the laboratory. Identification presented no problems, since no other species of Chione occurs more than rarely in the area, and there are no other species with which C. cancellata is likely to be confused. In discussing productivity, spawn production is used to include both eggs and sperm. 1969] Moore & Lopez: Ecology of Chione cancel/ala 133

100

1964 50 9

0

WIOO t9

100

c::::J UNRIPE r:::=:J RIPENING 50 RIPE -c::::J SPENT 0 J F M A M A S 0 N 0

FIGURE 1. Seasonal changes in condition of gonads of females.

GONADS Gonads were examined from unstained smears. When fully ripe the eggs lose their nuclear membrane and appear non-nucleate. Gonads con- taining nearly all non-nucleate eggs were never found, as they are in many species. In the whole series examined, only three individuals were seen with more than fifty per cent non-nucleate eggs, and one additional speci- men with more than 25 per cent. We have therefore described as ripe those individuals with more than ten per cent of non-nucleate eggs. Those with less than this percentage, but with generally large eggs, were described as ripening. Those with predominantly small eggs were described as un- ripe, and those with a few large eggs and much debris as spent. Males with testes full of active sperm were recorded as ripe, those with large gonads but little activity as ripening, those with large gonads but no activity as unripe, and those with only a few active sperm and much debris as spent. The smallest identifiable male was one with a shell length of 8.3 mm taken in December, and the smallest female (10.8 mm) was taken in 134 Bulletin oj Marine Science [19(1)

100

1964 50 d o

wlOO C)

100

c=J UNRIPE ~ RIPENING 50 _ RIPE

C=:J SPENT

o J F M AM J J AS 0 NO FIGURE 2. Seasonal changes in condition of gonads of males.

January. When between 14 and 16 mm in shell length, all individuals of both sexes develop a gonad. For seasonal comparisons of the tissue weight and gonadal size we selected a standard size of 23 mm. The spawning seasons are shown most clearly by the females, since in the males some ripe individuals are found throughout the year (Figs. 1, 2). In both 1965 and 1966 there was a definite winter spawning in the period January-February or January-March. The ovaries then ripened again, and there was a second spawning in the summer. The end of this summer spawning was caught in 1964, when it terminated in October. In 1965, it terminated in July, and in 1966, it had not yet commenced when the last sample was examined in July. The males, which are always more difficult to classify precisely, do not show a clear seasonal picture. For each sample, tissue weights were determined at a range of sizes, a regression was fitted to the data relating dry tissue weight to shell length cubed, and the weight of a standard-sized individual of 23 mm was read from this. Figure 3 shows the seasonal pattern of tissue-weight change in 1969] Moore & Lopez: Ecology of Chione cancellata 135

E Cl E

l- I (!) W ~ 110 W :J A---A = 1964 (J) (J) 0----0 = 1965 I- x·· ..·..····x = 1966 100 >- a: 0

90 JFMAMJJ ASOND FIGURE 3. Seasonal change in dry tissue weight of a 23-mm Chione in suc- cessive years. a standard animal. The winter spawning shows clearly in both 1965 and 1966, with about a 17 per cent weight loss in 1965. The graph indicates that the spawning commenced much earlier, in about September, in 1965- 66, and in this case the weight loss was 26 per cent. The summer spawning was not recorded completely in 1964, but was clear in the two succeeding years when it represented weight losses of 17 and 26 per cent respectively. Averaging the two years, the total annual loss of weight in spawning was 43 per cent. An attempt was also made to determine the gonadal changes from linear measurements of the gonad in situ. It was assumed that the total tissue weight of the animal was the sum of two components. The weight of the non-gonadal tissues was assumed to be a function of the cube of the shell length. The weight of the gonad was assumed to be a function of the cube of the gonadal length. From a series of measurements and weights the two partial regressions were computed. It was not feasible to determine the thickness of the gonad, but, on the same series, the width of the gonad also was measured and the partial regression of weight on the cube of the mean of width and length was computed. This yielded a slight improve- ment in correlation, so the extra measurement was included thereafter. Using these regressions, the weight of the gonad was estimated for the entire period of sampling. The seasonal pattern of these computed gonadal weights follows that of the total tissue weight only in a general way, and compares less well with the pattern of gonadal condition. Therefore, we calculated the error or 136 Bulletin of Marine Science [19(1)

50

40

llJ C> ct I- 30 Z llJ U a:: llJ a. 20

10

0 0 5 10 15 20 25 30 LENGTH (mm)

FIGURE 4. Percentage of parasitized individuals in relation to size. difference between the tissue-weight data and the calculated data for gonadal weight; the seasonal pattern of this very closely follows the pattern of tissue weight. We had thought that, as in some other animals, there might be a seasonal change in the size of some other organ such as the liver, and that this change might not be simultaneous with that of the gonad. The agreement between the error curve and the tissue-weight curve suggests that, if there is a seasonal change in weight of the liver, this is synchronized with the gonadal changes. It seems more likely, though, that the observed errors result from the length of the gonad not being repre- sentative of the mass of the gonad. Two years of observation are obviously insufficient for establishing a temperature relation, but possible associations may at least be noted. The first half of 1965 was markedly warmer than that of 1966. In the warmer year, the spring spawning was completed earlier, and the summer ripening also commenced earlier. We do not have data to show when the summer spawning was completed in both years. Finally, in the warmer year, in which spawning was earlier, the amount of spawning both spring and sum- mer was only about two-thirds of that in the colder year. Of 622 animals whose gonads were examined, 308 (49 per cent) were males, 248 (40 per cent) were females, and 66 (11 per cent), although large enough to be mature, could not be sexed. Of these 66, 48 were in- fected with trematode parasites in the gonad. Figure 4 shows the percentage of parasitized individuals in relation to 1969] Moore & Lopez: Ecology of Chione cancellata 137

50

25 1964

0

III C) «

~ ~ CL[]

50 1966 25 ------O+--.-----.-~-_r_-_.__-r__...-"""'T'"-_r_-_.__-..___ J F M A M J J A SON D. FIGURE 5. Seasonal variation in the percentage of individuals parasitized. size; there is a steady increase up to 50 per cent in the largest. There is a seasonal variation in the percentage of individuals parasitized, apparently with a maximum in the spring. This maximum also appeared to be greater in 1965-the warmer year-than it was in 1966, the colder year. The percentage increases in the larger animals, and there was some variation in the mean size of the animals used in the samples. By correcting for the effect of size on the percentage parasitized it is clear that the seasonal changes are real and not due to fluctuations in size (Fig. 5). The percentage of parasitization increased rapidly with increasing size. In the smallest sexable group, 15-20 mm in length, there were 46 per cent males, 45 per cent females, and 9 per cent unsexable. In the next size group there were 51 per cent males and only 36 per cent females, with the remainder unsexable. In the largest group, 25-30 mm in length, there were 48 per cent males, 37 per cent females, with the remainder unsexable. Some were, of course, unsexable because of being completely spent. It appears, though, that the sex ratio is normally 50: 50 and that in the older individuals this is modified by parasitic castration affecting the females more strongly than the males. As a verification of ripeness, fertilizations were attempted from time to 138 Bulletin of Marine Science [19(1)

35

30

25

20

15 1964

10

5

0

E 30 E ; 25 I- (!) 20 2: lAJ ....J 15 ....J ....J 10 lAJ :r:: l/) 5

0

30

25

20

15

10 I-----f 10 o % 5

0 J F M A M J J A 5 0 N 0

FIGURE 6. Size frequencies of Chione from Seaquarium flat, in I-mm groups and expressed as a percentage of N, for 1964, 1965, and 1966.

time. C. N. D'Asaro took over some of these and has followed the de- velopment through to metamorphosis (D'Asaro, 1967).

GROWTH Monthly samples were measured for size-frequency analysis for two years (Fig. 6). Because of the double breeding period, there are two peaks for 1969] Moore & Lopez: Ecology of Chione cancellata 139

2.0

1.5 0---0 = FIELD __ = TANK 1.0

0.5

1964

0.0

2.0 o 1\ 1\ E I \ I \ E I , 1.5 I \ IJ.J I '\

0.5

1965

1.5

1.0

0.5~

o.oJ , , , , , ,1966, JFMAMJJASOND

FIGURE 7. Comparison of growth of marked individuals in captivity and In the field. 140 Bulletin of Marine Science [19(1)

AUG 1964 l~B . ...

SEP MAR

J ~

OCT ] APR- ] MAY !] ~. ct ILl ~]~' J~j~~ 2 J DEC J~A" ~~

'~. J . ~.SEP :1 - . 8 13 18 23 28 33 8 13 18 23 28 33 LENGTH (mm)

FIGURE 8. Relation of growth per month to size in successive periods in the aquarium. each year-group, and only very much larger samples would have allowed tracing of the groups for any extended time. However, in 1965 the settle- ment of the animals spawned in the winter and again in the summer is clearly seen, and in 1966 the growth of the previous summer's brood and the commencement of settlement of the 1966 winter brood can be seen. The winter-spawned brood appears to reach a length of about 15 mm by autumn, while the summer-spawned brood reaches this length by the fol- lowing summer. Better growth data, particularly for older individuals, have been obtained from marked individuals returned to the shore or kept in aquaria. This is one of the few species which we have found to grow about as well in captivity as it does in the field (Fig. 7). For each month, curves (Fig. 8) 1969] Moore & Lopez: Ecology of Chione cancellata 141

35 SUMMER BROOD 30

25 m J[ 20 r e- 15 ~ 10 ~ ...... ~ 5 •...... "" C) "" Z 0 ILl J F M A M J J A S 0 N D ...J ...J ...J ILl ~ (/) 35 WINTER BROOD 30 ]I[ 25 I 20 o 15

10 ././- -~ ./ 5 ./ ./ ./ 0 JFMAMJ JA SON 0

FIGURE 9. Individual shell growth of a Chione through its first 4 years. were fitted freehand to the data for the aquarium-reared Chione to relate growth per month to shell size. The settling dates of winter and summer broods were assumed, and the first dates at which their sizes were clearly defined on the size-frequency graphs were selected. From the latter two values, monthly increments were read from the data in Figure 8. The re- sulting estimates of growth through their first four years are shown in Figure 9. By this time they have a shell length of about 25 mm. Individuals up to about 30 mm were found in the field, and a few tagged individuals over 25 mm showed a small growth, but in general it may be said that' growth ceases at about 25 mm. From the curves in Figure 8 we also extracted the growth rates for each month for individuals of a fixed size. The sizes selected were 5 mm, before gonads have developed; 15 mm, when they first mature; and 23 mm, to represent large older individuals. The immature individuals show a very 142 Bulletin of Marine Science [19(1)

1.0

E 0.5 ~m

E 0.0 '''5 " ••

2.0

1.5 15 mm

E 1.0 E

0.5

O.OJ 1965 1964

2.0

1.5

~ 1.0

0.5

1965 1964 00 J -~~-~~----- JFMAMJ J ASOND

FIGURE 10. Seasonal shell growth during 1964-65 for 5-, 15-, and 23-mm individuals. marked seasonal pattern of growth with a single peak in the summer (Fig. 10). Both sizes of mature individuals show a double growth period with peaks, one in the spring and the other in the summer. The growth is, as would be expected, slower in the larger sizes. A comparison can be made 1969] Moore & Lopez: Ecology of Chione cancellata 143

E C\ oS A 1964 I- 120 J: Cl lJJ ~ 110

.8 E E .6 J: I- 1964 ~ .4 o a: Cl .2

J F M A M J A SON 0

FIGURE 11. Composition of the seasonal patterns of shell growth and tissue weight for 1964 and 1965. of the seasonal patterns of shell growth and tissue weight (Fig. 11). There is a generally good correlation; shell growth is reduced when tissue weight is increased. Since the summer growth of the shell is reduced only in mature individuals, but is high in the immatures, it may be assumed that the summer reduction in shell growth is associated with gonadal condition. If this is the case, then it seems likely that the winter depression of growth of the shell may be in part associated with gonads. However, it occurs also in immatures, so is probably also the result of some response to en- vironmental change such as temperature. There is a correlation of 0.73 (less than 1 per cent) between shell growth and temperatures in the im- mature individuals.

COMPOSITION OF POPULA nON The frequency-distribution graphs in Figure 6 show a number of periods when either the winter or the summer brood can be clearly separated from all older individuals. From these an estimate of the mortality rate may be made if we can accept two rather doubtful assumptions. These are that the mortality rate is uniform throughout life, and that spat settlement is 144 Bulletin of Marine Science [19(1)

25 -. 120 l- X (!) jjj 15 ~ w ::l ~ 10

I-

5 o o J F M AMJJASON 0 FIGURE 12. Weight composition of population. equal in successive years. Of the two, the latter assumption is perhaps the more dangerous. However, we can compare the ratio of "0" to "1+" groups in two years, and for the two broods separately. A mortality rate of 42.5 per cent per year closely approximates the two year means for both broods, so we feel that we can accept this value for the purpose of discussion and not be seriously wrong. With regard to possible variation in mortality rate through life, the tagging experiments, while not yielding very extensive data, showed no indication of difference in recovery rate between small and large individuals. Assuming a settlement of 100 winter-brood spat in February-March and of another hundred summer-brood spat in August-September, and applying this mortality rate to them, we calculated the age composition of the re- sulting population through year-group "VI." These settlement dates are based on the observed spawning times and on an assumed larval duration of eleven to twelve days. The latter figure was kindly supplied by C. N. D'Asaro from laboratory experiments. From the data for seasonal growth, we calculated the lengths of individuals of both broods at monthly intervals through the sixth year. From the data on seasonal changes in tissue weight in relation to size, we similarly calculated the growth of individuals of both broods in terms of tissue weight. Finally, combining these data, we cal- culated the composition of the population by age-group and tissue weight. We can now see the significance of the successive year-groups in the stand- ing crop (Fig. 12). In their first year ("0" group) they contribute little to the biomass. The next two year-groups are of about equal importance, 1969] Moore & Lopez: Ecology of Chione cancellata 145

200 WINTER BROOD

150 f

100 E Ql ~E ~ 50 :I: TOTAL TISSUE WT. (!) NON GONAD TISSUE WT. ILJ ~ 0 ILJ SUMMER BROOD fJ)=> fJ) ~ 150

100

50

o o I JI J[ IlL ~ :m: FIGURE 13. Tissue growth of typical individuals of the winter and summer broods. and the succeeding year only little less. After this, the older individuals contribute little to the total. The graph also shows that there is some seasonal variation in biomass, associated with the two spawning periods, but that this is not very large. Figure 13 shows the growth, in terms of tissue weight, of typical in- dividuals of the winter and summer broods. The lower curves in each case represent the non-gonadal tissue, and the upper curves the total weight in- cluding gonads. They show that after about four years there is little growth in non-gonadal tissue, production being mainly restricted to gonads. Ani- mals at this age begin to constitute only a relatively small fraction of the total population. PRODUCTIVITY In a stable population it may be assumed that there are three major components of production. The first of these is maintenance, or the re- 146 Bulletin of Marine Science [19(1) placement of loss by mortality. We should be able to estimate this from the mortality figures. The second is the output of spawn, and this also we can estimate. The third is the output as dissolved organic matter, faeces, mucus, etc. Lacking information on any of these, our estimate of total production must be minimal. Using the standing crop in the above popu- lation and the mortality rate, we can calculate that the production of somatic tissue is 8.9 gm dry weight per year. A similar figure represents output of spawn, or a total of 17.8 gm. Spawn is equal to half of the total production. These figures are based on a population resulting from a settlement of a hundred spat at winter spawning and another hundred at summer spawn- ing. This corresponds to a mean standing crop, all ages included, of 365 individuals weighing 21.5 gm. In two other local species, the lamellibranch Tageius divisus (Fraser, 1967) and the heart urchin Moira atropos (Moore & Lopez, 1966), the annual productivity was found to be about equal to the standing crop. In Chione, it is somewhat less-83 per cent.

POPULATION DENSITY A survey was made of the intertidal mud flats near the Seaquarium in 1965 (Moore et ai., 1968). For the entire shore between high and low water the mean density of Chione was 28.3 per square meter, and the maxi- mum density was 162 per square meter. In the survey of the sublittoral area of the bay (McNulty et al., 1962), the mean density in four succes- sively coarser categories of sediment was 0.31, 0.36, 0.83, and 0.00 per square meter. In two years of study of selected muddy-bottom commu- nities, the mean density of area A was 0.63, and that of area B, 1.74. If a typical sublittoral community has a density of one Chione per square meter, the corresponding annual production would therefore be 4.88 mg. For a rich intertidal community of 162 per square meter it would be 7.9 gm. Chione is much more abundant in grass than in clear areas. The above sublittoral counts refer only to bare areas, so are probably considerably too low to be representative of the bay as a whole. Two sublittoral areas of patchy Thaiassia near Featherbed Bank had densities of 35 and 19 speci- mens of Chione per square meter respectively. The bay from Rickenbacker Causeway down to the Arsenicker Islands and Cutter Bank has an area of 498 X Ion square meters. If we assume that one-third of this is covered with grass, and that the grassy areas have a population density of only 10 specimens of Chione per square meter, then a first approximation of the productivity for the whole bay would be eighty metric tons per year, of which half would be in the form of spawn.

BEHAVIOR In the field, specimens of Chione were found buried to a maximum depth of 30 em, but were usually between the surface and 15 em. There did 1969J Moore & Lopez: Ecology of Chione cancellata 147 not appear to be any tendency for the smaller ones to be nearer the sur- face, as there is in some other forms, such as Anodontia. Frequently, under natural conditions, the tip of the shell is exposed, and sometimes this may have algae such as Penicillus attached. These algae could hardly remain if they were buried deeply or frequently. When Chione was placed on the surface of the mud, the foot was pro- truded and the shell turned to a vertical position. It usually succeeded then in burrowing into the sediment, but did this slowly, and took about twenty minutes to complete the operation. When kept in tanks, the specimens of Chione left a furrow behind them if they moved about below the surface. Advantage was taken of this to record the extent of their migrations. When brought in from the field, which involves a considerable disturbance, they would wander about for several days. Such movement occurred both in the daytime and at night. The trail was meandering, but totalled as much as 13 em in an hour and 140 em in 15 hours. By contrast, individuals which were established in the tanks frequently did not move about at all, and others only a few centi- meters a day. However, any disturbance induced wandering. Even addi- tion of sediment to the water had this effect. During their wandering, the individuals of Chione showed no tendency to aggregate, as do those of Anodontia. On the shore, Chione tends to orient with its long axis at right angles to the beach, in which position it would no doubt offer the least resistance to the waves. In tanks, Chione did not appear to be sensitive to movement of the water, nor to increase in illumination. However, it reacted sharply to a shadow by retraction of its siphons. The sensitivity appeared to be concentrated in the papillae at the edge of the siphons, since a small shadow applied there induced retraction. Records of inshore temperatures are available from tidal-gauge data (Coast and Geodetic Survey, 1965). These indicate that, over its geo- graphic range, C. cancel/ala can tolerate a mean winter minimum of 6.7°C at the northern limit and a summer maximum of 31.1°C at its southern limit. Both of these could undoubtedly be more extreme in some shallow locations. In the exceptionally cold winter of 1957-1958, Chione may have suffered a kill at Miami, but the densities were too small to be certain.

SUMARIO ECOLOGIA DE Chione cancellata Chione cancellata se encuentra en la zona sublitoral y entre las lfneas de las mareas. Madura al alcanzar una longitud de un os quince milimetros a la edad de un ano. Crece poco despues de los cuatro anos. Chione se reproduce dos veces al ano, en invierno y en verano. El crecimiento de la concha esta positivamente en correlaci6n con la temperatura en los no 148 Bulletin of Marine Science [19(1 ) maduros, pero disminuye en el verano en los adultos. La productividad anual es alrededor del 83 por ciento de la cosecha potencial y la mitad de esta productividad es en forma de huevas. Una comunidad numerosa de la zona entre las mareas produce un peso seco de 7.9 gm por metro cuadrado por ano. Se da una relaci6n del habitat y comportamiento de esta especie.

LITERATURE CITED ABBOTT, R. TUCKER 1954. American Seashells. D. Van Nostrand Co. Inc., New York, xiv + 54 pp., 100 text-figs., 40 pIs. COAST AND GEODETIC SURVEY 1965. Surface water temperature and salinity, Atlantic Coast. C. & G. S. Publication No. 31-1, second edition. Govt. Printing Office, Wash- ington, D. C., 88 pp. DALL, WILLIAM H. 1903. Synopsis of the family Veneridae and of the North American recent species. Proc. U. S. Nat. Mus., 26(1312): 335·412. D'AsARO, CHARLES N. ] 967. The morphology of larval and postlarval Chione cancel/ala Linne (Eulamellibranchia: Veneridae) reared in the laboratory. Bull. Mar. Sci., 17(4): 949-972. FRASER, THOMAS H. 1967. Contributions to the biology of Tagelus divisius (Tellinacea: Pele- cypoda) in Biscayne Bay, Florida. Bull. Mar. Sci., 17(1): 111-132. McNULTY, J. K., R. C. WORK AND H. B. MOORE 1962. Level sea bottom communities in Biscayne Bay and neighboring areas. Bull. Mar. Sci. Gulf & Carib., 12(2): 204-233. MOORE, HILARY B., L. T. DAVIS, T. H. FRASER, R. H. GORE, AND NELIA N. LOPEZ 1968. Some biomass figures from a tidal flat in Biscayne Bay, Florida. Bull. Mar. Sci., 18(2): 261-279. MOORE, HILARY B. AND NELIA N. LOPEZ 1966. The ecology and productivity of Moira atropos. Bull. Mar. Sci., 16(4): 648-667.