Direct Observation of Bay Scallop Spawning in New York Waters

BULLETIN OF MARINE SCIENCE, 82(2): 213–219, 2008

NOTE

DIRECT OBSERVATION OF BAY SCALLOP SPAWNING IN NEW YORK WATERS

Stephen T. Tettelbach and Andrew Weinstock

Rapid increase in water temperature is cited as the major environmental cue for spawning induction in bay scallop, Argopecten irradians (Lamarck, 1819), populations (Sastry, 1963; Barber and Blake, 2006) and serves as the standard method for inducing spawning of mature bay scallops in the hatchery (Loosanoff and Davis, 1963). Other documented cues for triggering bay scallop spawning include temperature decrease (Barber and Blake, 2006) and mechanical disturbance (K. Tetrault, Cornell Cooperative Extension, pers. comm.). Other pectinid species respond to these same spawning cues, as well as addition- al stimuli. Spawning in natural populations of Placopecten magellanicus (Gmelin, 1791) is known to be induced by temperature increases, including sharp temperature spikes due to downwelling of warmer waters (Bonardelli et al., 1996), and has been correlated with lunar periodicity (Parsons et al., 1992). Spawning of Pecten maximus (Linnaeus, 1758) (Tang, 1941; Mason, 1958; Stanley, 1967) and Chlamys opercularis (Linnaeus, 1758) (Amirthalingam, 1928) has also been associated with lunar cycles. Desrosiers and Dubé (1993) induced spawning of P. magellanicus in the laboratory by mechanical stimulation using flowing seawater. Spawning of P. magellanicus in the field was correlated with physical disturbance associated with high winds and rough seas (Naidu, 1970). Similarly, spawning of Chlamys varia (Linnaeus, 1758) in Ire- land was associated with onshore winds and elevated temperatures (Minchin, 1992), while spawning of Chlamys islandica (Muller, 1776) in Canada may be triggered by phytoplankton blooms (Arsenault and Himmelman, 1998). Direct observations of scallop spawning in the field are relatively rare. Minchin (1992) observed spawning of C. varia during afternoon and early evenings in Ireland on over 20 occasions from 1976–1988; in some instances, spawning was seen on successive days. Styan and Butler (2003) observed spawning of Chlamys asperrima (Lamarck, 1819) in South Australia on one occasion, at night, over a period of ~3.5 hrs; subsequent spawning was not observed later that night or the next day (4, 8, or 16 hrs later). We are unaware of any published reports of direct observations of bay scallop spawning in the field. Here, we report an opportunistic observation of mass spawning of northern bay scallops, Argopecten irradians irradians (Lamarck, 1819), in waters of eastern Long Island, New York, USA.

Materials and Methods

Observations reported here were made as part of a 2-yr study to evaluate different methods of deploying bay scallop spawner sanctuaries (Tettelbach et al., 2007). Scallops were spawned at hatcheries in Southold and East Hampton, New York, in May–June 2004 and subsequently overwintered at Shelter Island (SI group) and East Hampton (EH group), respectively. Scallops were then planted in Northwest Harbor, East Hampton, New York (41°01.806´N, 72°14.596´W, Fig. 1) between 28 March–1 April 2005 and monitored through late October 2005. Our direct observations of scallop spawning were made opportunistically while diving on 7 June 2005;

Figure 1. Map of Northwest Harbor/Sag Harbor, East Hampton, New York, USA, showing the location of the study site (*) at 41°01.806´N 72°14.596´W and regional map showing location relative to the Long Island/southern New England area of the northeast USA. digital photographs of spawning scallops were taken with a 5.0 Megapixels Sony Cybershot digital camera (Model No. DSC-P10). The degree of spawning synchrony in the scallop population, i.e., the proportion of scallops releasing gametes at any given moment, was roughly estimated by integrating visual observations of the number of scallops seen spawning at one time with estimates of underwater field of vision (lateral visibility was ~1.5–1.8 m) and mean scallop density (56.1 ± 23.6 ind m–2, SD) on 7 June 2005. Mean scallop height on this day was 42.5 mm (SD = 4.3). Observations of spawning on 7 June were analyzed in relation to data we had been collect- ing as part of our ongoing study on physical (water temperature, wind speed/direction, wave height, and lunar phase) and biological factors (including chlorophyll concentrations and reproductive condition of scallops in our planted population). Water temperature was recorded NOTES 215 every 6 hrs from 30 March to 28 October 2005 with an automated, submersible temperature logger (Onset HOBO® Model No. 8) attached to a cinder block at a depth of 1.3 m at mean low water. Pertinent wind speed/direction data were obtained from available databases (Weather Underground, 2005) while wave heights in Northwest Harbor were visually estimated. In our analyses of the potential association of scallop spawning with wind events, easterly (NE, E, SE) winds were considered to be comparable to calm conditions (i.e., wind speed = 0) as they would be expected to contribute to wave action and mechanical stimulation of scallops in only a negligible way due to the location of the study site at only ~75–100 m from the eastern shore of Northwest Harbor. Total Chl-a concentrations were monitored every 2–3 wks fol- lowing the methods of Parsons et al. (1984). From early May–late October 2005, biweekly monitoring of reproductive condition (gonad dry weight (GDW): Barber and Blake, 2006) was done for each of the two scallop groups (SI and EH).

Results and Discussion

Mass spawning of A. i. irradians was directly observed and photographed (Fig. 2) on 7 June 2005 between ~1530–1700 hrs. Scallops from both planted groups were seen spawning over the entire expanse of the 100 m by 25 m planting area, at depths ranging from ~1.3–3 m. Both eggs and sperm were seen being shed into the water; small groups of scallops, which were watched for up to 5 min, all released gametes by opening and closing their valves at 10–30 s intervals. The degree of spawning synchrony in the scallop population was estimated to have been roughly 3%–12%. Apart from the instances of gamete release, many scallops were observed to gently rock in place with the northward flowing current. Observed spawning occurred on an ebbing tide (low tide was at ~1705 hrs), 1 d after a new moon, and coincided with a sharp spike in water temperature and an increase in wave action. On 7 June 2005, water temperature increased from 18.28 °C at

Figure 2. Spawning bay scallops, Argopecten irradians irradians, Northwest Harbor, East Hamp- ton, New York at 1600 hrs, 7 June 2005. Note the cloud of eggs above the individual in the left center of the field. Approximate field width = 18 cm. Photograph by S. Tettelbach. 216 BULLETIN OF MARINE SCIENCE, VOL. 82, NO. 2, 2008

0400 hrs to 19.42 °C at 1000 hrs to 23.24 °C at 1600 hrs; the latter temperature represented the highest level recorded to that point in the spring (Fig. 3A). These temperatures correspond very well to reported levels at which bay scallop spawning occurs in New York (Bricelj et al., 1987; Tettelbach et al., 1999, 2002), but the coincidence of the mass spawning with the temperature spike on 7 June (3.82 °C in 6 hrs; 4.96 °C in 12 hrs) suggests that this was likely the major thermal cue (Barber and Blake, 2006). From March–October 2005, the mean daily temperature variation was 1.82 °C; the 4.96 °C increase on 7 June represented the greatest temperature change recorded on any single day during the study period (Fig. 3A). The temperature spike on 7 June may also have acted in concert with mechanical disturbance due to strong winds and wave action to induce scallop spawning. Aver- aged wind speeds on 7 June, recorded ~8 km to the S at the East Hampton Airport, ranged from 22.2 km hr–1 to 29.6 km hr–1 between 0950–1150 hrs, then increased from 22.2 km hr–1 at 1450 hrs to 31.5 km hr–1 at 1650 hrs (Fig. 3B: Weather Under- ground, 2005). These were well above average daytime wind speeds (mean = 17.1 km hr–1, SE = 0.52) for June 2005 and exceeded the averaged daily maximum wind speed (mean = 20.5 km hr–1; SE = 0.82) for the period of 30 March–28 October 2005 (Fig. 3B: Weather Underground, 2005). Winds consistently blew from the SW on 7 June 2005 (Weather Underground, 2005) and, with a SW fetch of > 4 km (Fig. 1), wave heights at the planting site were visually estimated to have increased from < 15 cm at 1000 hrs to 30–50 cm by the time scallop spawning was observed at 1530 hrs on 7 June—thus causing the gentle rocking of scallops. The average wave height for this area in June is ≤ 30 cm (Tettelbach, unpubl. data). Spawnings of C. varia that Minchin (1992) directly observed in the field were similarly associated with onshore winds and elevated temperatures. In contrast, however, the spawning of C. asperrima which Styan and Butler (2003) directly observed occurred under low water flow conditions and at a time of year well after when peak ripeness is ordinarily seen at that location. The fact that the spawning we directly observed on 7 June occurred 1 d after a new moon is interesting but further data are required to determine if there is a correla- tion between bay scallop spawning and lunar periodicity. There is no evidence that spawning on 7 June coincided with a phytoplankton bloom, as chlorophyll a levels ranged from 2.8–4.5 µg L–1 between 30 May–28 June—close to the March–October 2005 average of ~3.4 µg L–1 (C. Gobler, Stony Brook University, unpubl. data). While there is probably no specific temperature range, per se, at which spawning of scallops occurs, as this depends on acclimation history, a minimum threshold temperature appears to be necessary for spawning to be initiated (Barber and Blake, 2006). Spawning appears to have first occurred in our scallop populations between 23 May and 6 June 2005—as evidenced by a marked decline in GDW of the EH scallop group (Fig. 3C). Spawning may even have commenced on 23 May, when there was a 3.05 °C temperature spike from 14.47–17.52 °C between 0400–1600 hrs (Fig. 3A) and S wind speeds increased from 0 to 14.8 km hr–1 between 0945–1359 hrs (Weather Underground, 2005). Additionally, during the 8-d period between 30 May and 6 June 2005, when water temperature ranged from 15.62–20.57 °C, there were temperature spikes of ≥ 2.28 °C on seven of those days (Fig. 3A) that coincided with maximum wind speeds of 14.8–33.3 km hr–1 (Fig. 3B) which may have prompted mechanical stimulation of scallops. Bricelj et al. (1987) inferred that bay scallop spawning occurred at temperatures as low as 14 °C in populations in and around Northwest NOTES 217

Figure 3. (A) Water temperature recorded at ~1.3 m depth (at MLW) in Northwest Harbor, East Hampton, New York from 30 March–28 October 2005; measurements were taken every 6 hrs. (B) Daily maximum wind speed (km hr–1) recorded at the East Hampton, New York airport, ~ 8 km to the S of the study site, as reported by Weather Underground (2005): 28 March–28 October 2005. Readings were taken at ≥ 1 hr intervals between 0450–1955 hrs. (C) Temporal changes in gonad dry weight (GDW) of bay scallops, Argopecten irradians irradians, after free-planting in Northwest Harbor, East Hampton, New York in late March/early April 2005. Data points repre- sent mean values for GDW ± 1 SE; n = 16–20 scallops per group, per sample date. SI and EH = scallops overwintered at Shelter Island and East Hampton, respectively, prior to planting.

Harbor, New York. The mass spawnings of C. varia observed by Minchin (1992) occurred only at temperatures > 14 °C (temperature increases on these days ranged from 0.3–2.1 °C); only isolated spawning was seen at temperatures < 14 °C and fol- lowing declines in temperature. All three scallop spawning periods (23 May–21 June; 13–27 July; 8 August–9 Sep- tember) that can be inferred from marked declines in GDW (Fig. 3C) coincided with periods during which sharp temperature increases occurred on one or more days; in some cases these were accompanied by high winds. For the first period, in addition to the temperature/wind data mentioned above, temperature spikes of 3.05–3.82 °C (Fig. 3A) occurred on four different days between 8–12 June and were accompanied by winds of 22.2–33.3 km hr–1 (Fig. 3B). On 20 and 21 July, the greatest temperature spikes which were recorded during the second spawning period (3.11 and 3.51 °C, 218 BULLETIN OF MARINE SCIENCE, VOL. 82, NO. 2, 2008 respectively) were accompanied by maximum wind speeds of 22.2 and 18.5 km hr-1. It should also be noted that the highest single temperature (27.91 °C) recorded during the March-October study period occurred on 21 July. Between 8 August–9 Septem- ber, temperature spikes of 2.71, 2.32, and 2.32 °C occurred on 17, 18, and 20 August, respectively, and were accompanied by relatively lighter maximum daily winds of 18.5, 0, and 13.5 km hr–1. Desrosiers and Dubé (1993) concluded that the synergistic effects of mechanical and thermal stimulation may contribute to a stronger and more rapid spawning response in male P. magellanicus in the laboratory. While we can only speculate on the specific dates when spawning occurred during the three periods in 2005 our direct observation of bay scallop spawning on 7 June suggests that, when individuals are fully ripe, the occurrence of a sharp spike in water temperature coupled with wind events that promote increased wave action and mechanical disturbance prompt mass spawning in populations of A. i. irradians.

Acknowledgments

We thank J. Thiel and M. Cammarota for their assistance in the field and C. Petti and S. Schott for assistance with preparation of the figures. Funding for the field project was sup- plied via a New York State Wildlife Grant, through the New York State Department of Envi- ronmental Conservation and Cornell Cooperative Extension of Suffolk County, Riverhead, New York.

Literature Cited

Amirthalingam, C. 1928. On lunar periodicity in reproduction of Pecten opercularis near Plym- outh in 1927–1928. J. Mar. Biol. Assoc. U.K. 15: 605–641. Arsenault, D. J. and J. H. Himmelman. 1998. Spawning of the Iceland Scallop (Chlamys islandica Muller, 1776) in the northern Gulf of St. Lawrence and its relationship to temperature and phytoplankton abundance. Veliger 41: 180–185. Barber, B. J. and N. J. Blake. 2006. Reproductive physiology. Pages 357–416 in S. E. Shumway and G. J. Parsons, eds. Scallops: biology, ecology & aquaculture, Second Edition. Elsevier, New York. Bonardelli, J. C., J. H. Himmelman, and K. Drinkwater. 1996. Relation of spawning of the giant scallop, Placopecten magellanicus, to temperature fluctuations during downwelling events. Mar. Biol. 124: 637–649. Bricelj, V. M., J. Epp, and R. E. Malouf. 1987. Intraspecific variation in reproductive and somatic growth cycles of bay scallops Argopecten irradians. Mar. Ecol. Prog. Ser. 36: 123–137. Desrosiers, R. R. and F. Dubé. 1993. Flowing seawater as an inducer of spawning in the sea scallop, Placopecten magellanicus (Gmelin, 1791). J. Shellfish Res. 12: 263–265. Loosanoff, V. L. and H. C. Davis. 1963. Rearing of bivalve mollusks. Adv. Mar. Biol. 1: 1–136. Mason, J. 1958. The breeding of the scallop Pecten( maximus L.) in Manx waters. J. Mar. Biol. Assoc. U.K. 37: 653–671. Minchin, D. 1992. Multiple species, mass spawning events in an Irish sea lough: the effect of temperatures on spawning and recruitment of invertebrates. Invert. Reprod. Dev. 22: 229–238. Naidu, K. S. 1970. Reproduction and breeding cycle of the giant scallop Placopecten magellanicus (Gmelin) in Port au Port Bay, Newfoundland. Can. J. Zool. 4: 1003–1012. Parsons, G. J., S. M. C. Robinson, R. A. Chandler, L. A. Davidson, M. Lanteigne, and M. J. Dadswell. 1992. Intra-annual and long-term patterns in the reproductive cycle of giant scallops Placopecten magellanicus (Bivalvia: Pectinidae) from Passamaquoddy Bay, New Brunswick, Canada. Mar. Ecol. Prog. Ser. 80: 203–214. NOTES 219

Parsons, T. R., M. Takahashi, and B. Hargrove. 1984. Biological oceanographic processes. Third Edition. Pergamon Press, New York. Sastry, A. N. 1963. Reproduction of the bay scallop Aequipecten irradians Lamarck. influence of temperature on maturation and spawning. Biol. Bull. 125: 146–153. Stanley, C. A. 1967. The commercial scallop, Pecten maximus in Northern Irish waters. Ph.D. thesis, Queens University of Ireland, Belfast. 111 p. Styan, C. A. and A. J. Butler. 2003. Asynchronous patterns of reproduction for the sympatric scallops Chlamys bifrons and Chlamys asperrima (Bivalvia:Pectinidae) in South Australia. Mar. Freshw. Res. 54: 77–86. Tang, S. F. 1941. The breeding of the escallop Pecten( maximus L.) with a note on the growth rate. Proc. Transl. Liverpool Biol. Soc. 54: 9–28. Tettelbach, S. T., C. F. Smith, P. Wenczel, and E. Decort. 2002. Reproduction of hatchery-reared and transplanted wild bay scallops, Argopecten irradians irradians, relative to natural populations. Aquacult. Int. 10: 279–296. ______, C. F. Smith, R. Smolowitz, K. Tetrault, and S. Dumais. 1999. Evidence for fall spawning of northern bay scallops Argopecten irradians irradians (Lamarck, 1819), in New York. J. Shellfish Res. 18: 47–58. ______, D. Bonal, A. Weinstock, D. Barnes, G. Rivara, C. Fitzsimons-Diaz, and J. Car- roll. 2007. Comparison of different deployment strategies for bay scallop spawner sanctuaries in New York. J. Shellfish Res. 26: 670. Weather Underground. 2005. East Hampton, New York (11937) Conditions & Forecast: Weather [Internet]. Ann Arbor, MI; The Weather Underground, Inc. © 2005, 10 October 2007. Available from: http://www.wunderground.com/history/airport/KHTO/2005/6/7/ DailyHistory.html

Date Submitted: 6 March, 2007. Date Accepted: 15 January, 2008.

Addresses: (S.T.T., A.W.) Biology Department, C.W. Post Campus of Long Island University, 720 Northern Blvd., Brookville, New York 11548. Corresponding Author: (S.T.T.) E-mail: .