INTERNATIONAL COUNCIL FOR ICES CM 2009/B:16 THE EXPLORATION OF THE SEA Beyond Geolocation: Inferring and explaining the behavior of tagged fish

Winter Flounder Movements in the Southern

Gregory R. DeCelles and Steven X. Cadrin NOAA/Umass Cooperative Marine Education and Research Program School for Marine Science and Technology

A two-year acoustic tagging experiment was conducted in the estuary to examine seasonal movement patterns of adult winter flounder. During the first year of the study, 47 individuals were fitted with acoustic transmitters and tracked using an array of 15 Vemco receivers. During the second year of the study, the passive array was expanded from 15 to 30 receivers and an additional 25 flounder were tagged within the array, allowing more direct tests of alternative hypotheses about spawning migrations. Telemetry data suggests that seasonal movements within the estuary were strongly associated with water temperature. A proportion of tagged flounder migrated into the estuary in the spring as water temperature increased, while others remained in coastal waters. Of those individuals that entered the estuary in the spring, the majority emigrated to coastal waters in June, when water temperatures in the estuary exceeded 15oC. A small portion (n=5) of tagged fish were detected reentering the estuary in autumn, as water temperatures decreased to less than 15 oC. Tagged flounder exhibited spatially and temporally diverse movements, and it appears that sympatric, contingent spawning groups of winter flounder may occur within this relatively small geographic area.

Keywords: winter flounder, Pseudopleuronectes americanus, acoustic telemetry, contingent

Contact Author: Greg DeCelles, NOAA/Umass CMER Program, School for Marine Science and Technology, 200 Mill Rd. Suite 325, Fairhaven, MA 02719 U.S.A. [tel: +1 508 910 6393 email: [email protected]]

1 Introduction

Knowledge of seasonal changes in the distribution and behavior of individuals within populations is a crucial step in understanding population structure (Metcalfe, 2006). Acoustic telemetry offers researchers the ability to better understand fish behavior and migration, and ultimately allows for contingent groups within populations to be recognized (Secor, 1999). Acoustic tags also allow unprecedented opportunities to understand the amount of connectivity between estuarine and coastal populations (Able, 2005). Another advantage of this technology is that data acquisition is not dependent upon the recapture of tagged individuals by the fishery. In this study we sought to understand the migratory patterns of winter flounder in the southern Gulf of Maine using acoustic telemetry. The miniaturization of acoustic transmitters has allowed for the study of flatfish biology and migration. Telemetry has been successfully used to study many flatfish species including; plaice (Greer Walker et al., 1978), summer flounder (Sackett et al., 2007), and sole (Greer Walker et al., 1980). More specifically, this technology has been used to investigate winter flounder spawning habitat (Pereira et al., 1994), movement patterns (John Manderson, NOAA, personal communication) and habitat use by juveniles (Elizabeth Fairchild, University of New Hampshire, personal communication). In the coastal waters of the U.S., winter flounder are managed as three stocks; Gulf of Maine, Southern New England/Mid-Atlantic (SNE/MA) and Georges Bank. Individuals in the Gulf of Maine and SNE/MA stocks are resident in coastal and estuarine waters. Flounder in the Georges Bank stock remain offshore throughout their entire life cycle. The seasonal distribution of winter flounder in the SNE/MA stock have been studied using a series of mark-recapture experiments (e.g. Perlmutter, 1947; Saila, 1961; Powell, 1989), and this stock is considered to be dependent upon estuarine habitats (Able and Fahay, 1998). There has been far less research on winter flounder in the Gulf of Maine, relative to the SNE/MA stock. As a result, there is considerable uncertainty regarding the movement and spawning patterns of winter flounder in the Gulf of Maine stock. Traditionally, winter flounder in the Gulf of Maine were presumed to spawn exclusively in estuarine habitats (Bigelow and Schroeder, 1953). However, this paradigm may have arisen due to observations in the SNE/MA stock area, or due to the relative ease of sampling flounder in estuaries, rather than coastal habitats. More recent data suggests that some flounder in the Gulf of Maine are using coastal waters as spawning grounds, rather than estuaries. Due to the demersal and adhesive nature of winter flounder eggs (Pereira et al., 1999), dispersal of eggs is limited, and ichthyoplankton tows capturing their eggs can be used to infer spawning locations. Winter flounder eggs have been sampled in coastal locations of Bay and Bay (Lux and Kelly, 1982). The ages of eggs sampled in Plymouth Bay, Massachusetts suggested that a substantial proportion were produced by coastal spawning events (Chau and Pearce, 1977). Howe and Coates (1975) hypothesized that coastal spawning groups may exist based upon their observations of adult fish captured in coastal and offshore waters during the spawning season. In addition, the Massachusetts Division of Marine Fisheries Industry-Based Survey commonly captured adult winter flounder in coastal waters in March and April in

2 2005, 2005 and 2007 (Hoffman et al., 2007; Figure 1). The presence of adult fish in coastal waters in March and April is significant, because these are considered the peak spawning months for winter flounder in the Gulf of Maine (DeCelles and Cadrin, 2007). Contingents are defined as groups of fish that exhibit divergent migratory patterns or habitat use (Secor, 1999). In this paper, we refer to contingents as adults that spawn in either coastal or estuarine waters. The presence of contingent structure within the Gulf of Maine stock will have important ramifications for population structure and the identification of Essential Fish Habitat. Spatial structure may provide fish populations with enhanced stability and resilience due to variable survival of early life history stages in different habitats (Kerr et al., 2009). For winter flounder, which spawn demersal eggs, the conditions encountered by the early life history stages are largely determined by the locations where adults spawn. The progeny of estuarine and coastal spawning flounder will likely exhibit different larval transport trajectories and survival. In this study we tracked the movements of adult winter flounder using acoustic transmitters and a moored array of acoustic receivers. Plymouth Bay and the adjacent Plymouth , Duxbury Bay, Kingston Bay estuary (hereafter Plymouth estuary) in the southern Gulf of Maine were chosen as the study site. Winter flounder is a dominant member of the groundfish community in the Plymouth estuary (Lawton et al., 1984), and the area serves as an important nursery habitat for juvenile winter flounder. The Plymouth estuary is a known spawning area for winter flounder (Normandeau Associates, 2001) with peak spawning typically observed in March and April. In addition, the coastal waters of Plymouth Bay have been identified as an area where coastal spawning likely occurs (Chau and Pearce, 1977; Marine Research Inc., 1986). Furthermore, the geography of the Plymouth estuary allowed us to achieve adequate sampling coverage using relatively few acoustic receivers. The goal of this study was to characterize the seasonal movement patterns of adult winter flounder in Plymouth Bay and the Plymouth estuary using acoustic telemetry. In order to investigate the hypothesis of coastal spawning, we sought to identify probable spawning habitats using the observed movements of tagged individuals during the spawning season. Gaining a better understanding of the spawning habits of winter flounder in the Gulf of Maine area may improve management of this species, aid in conservation efforts and allow further insight into the population and stock structure of this species. This information is critical in light of Essential Fish Habitat requirements.

Materials and Methods

Study Site

The Plymouth estuary and the adjacent Plymouth Bay are located in the southern portion of the Gulf of Maine (Figure 2). The Plymouth estuary is bordered on its seaward side by two barrier beaches. Tidal exchange between the Plymouth Estuary and Plymouth Bay occurs through a 2,020m opening between Saquish Head and the northern extremity of Plymouth Beach. Approximately 66% of the water in the Plymouth estuary is replaced during each tidal cycle (Iwanowicz et al., 1974). Extensive sand and mud flats are exposed at mean low water when the surface area of Plymouth estuary is reduced

3 from 10,057 acres to 5,465acres (Iwanowicz et al., 1974). Plymouth Bay is bordered on its eastern extent by . The average depth within Plymouth estuary is 3.3m at mean high water and 2.1m feet at mean low water, and the average tidal amplitude is 2.9m (Iwanowicz et al., 1974). A deeper is present between Saquish Head and Plymouth Beach, where depths reach nearly 26m. The major sources of freshwater input to the Plymouth Estuary are; Back River, Bluefish River, , and Eel River.

Acoustic Telemetry

In total, 72 adult winter flounder were fitted externally with acoustic transmitters (Model V92L, 69kHz, 9mm X 21mm, Vemco Ltd.) between 2007 and 2009 (Figure 3). The transmitters had an expected battery life of 384 days (Matthew Holland, Vemco Ltd., personal communication), allowing each fish to be tracked for approximately one year. Prior to the first year of tagging in 2007, we planned to release 47 tags in two discrete batches. The first group of tags (n=24) were to be deployed in the coastal waters of Plymouth Bay during the winter of 2007, prior to the spawning season. We planned to release the second batch of tags (n=23) on spawning fish inside the Plymouth estuary during the months of March and April, 2008. In November of 2007, 24 pre-spawning flounder were tagged in Plymouth Bay, approximately 5km from the mouth of the Plymouth estuary (Figure 4). Three tagged flounder were observed to be gravid females at the time of release. Repeated efforts to capture spawning adult flounder within the estuary during March, April and early May of 2008 were unsuccessful (Table 1). Adult fish were not captured until late May and June of 2008, when 23 adult flounder were tagged within the PDK estuary (Figure 4). In the second year of the study, an additional 25 flounder were tagged in Plymouth Bay between December, 2008 and May, 2009 (Figure 5). Winter flounder were captured in Plymouth Bay and the Plymouth estuary using either a small otter trawl, a commercial trawl vessel (F/V Zachary Nicolas) or using hook and line. Each fish was measured to the nearest centimeter, and only adult fish (> 27cm) in good or excellent condition were fitted with acoustic tags. Fish were held onboard for observation following tagging until they were deemed healthy enough for release. All fish were released in close proximity to the capture site in order to minimize tagging- induced behavior. The peritoneal cavity of winter flounder is too small to allow the transmitters to be surgically implanted into the animals. Therefore, the transmitters had to be externally attached to the flounder. A novel attachment method was developed for this study. Acoustic transmitters were inserted to a harness of 9/16” soft latex tubing and secured inside the harness using two-part epoxy. Two nickel tagging pins were passed upwards from the blind side of the fish through the dorsal musculature. The harness was then secured to the nickel pins on the eyed side of the fish using plastic earring backings (Figure 6). The tagging procedure took an average of 2-3 minutes per fish. A laboratory holding study indicated 100% retention and survival over a seven month period. In addition, a separate holding study conducted at the University of New Hampshire indicated that the tag attachment method did not interfere with the swimming or spawning behavior of tagged fish (Elizabeth Fairchild, personal communication).

4 Flounder tagged in the first year (n=47) were tracked throughout the Plymouth estuary using a moored array of 15 wireless receivers (Model VR2 and VR2W, Vemco Ltd.; Figure 4). Preliminary range testing was conducted within the study site and the receivers were found to be functional at a radius of at least 250m. Receivers were moored one meter above the benthos. Six receivers (I, J, L, M, N and O) were configured as a parallel curtain array that spanned the mouth of the PDK estuary. Parallel curtain arrays are advantageous because they allow the direction of movement for each fish to be obtained (Heupel et al., 2006). Receivers within the parallel curtain were positioned to ensure that overlap existed between the detection radii of adjacent receivers. This allowed the movements of tagged fish between the Plymouth estuary and Plymouth Bay to be recorded precisely. The movements of tagged fish within the Plymouth estuary were tracked using nine receivers positioned in a non-overlapping grid array. These receivers were placed within the channels of the Plymouth estuary to maximize their detection radii. Data recorded by the receivers on each detection included; date, time, receiver number and station, and tag identity. Prior to the release of the second year of tags (n=25) in September of 2008, the receiver array was expanded from 15 to 30 wireless receivers (Model VR2 and VR2W, Vemco Ltd., Figure 5). A curtain of 10 receivers (P-Y) was deployed that spanned the mouth of Plymouth Bay, from Gurnet Point in Duxbury southward to Rocky Point in Plymouth. This allowed us to track the movement of tagged flounder between Cape Cod Bay and Plymouth Bay. An additional five receivers (Z-DD) were placed within the reaches of the PDK estuary. Prior to their retrieval in 2009, six of the thirty acoustic receivers were lost. Receiver losses were likely due to boat traffic or interactions with commercial fishing gear. Receivers P and Y were lost from the outer gate between Cape Cod Bay and Plymouth Bay. Therefore, the detection efficiency of this receiver gate may have been less than 100%. In addition, receivers I, M and O were lost from the parallel curtain between Plymouth Bay and the Plymouth estuary. Subsequently, receiver G was moved from the “Cowyard” and placed adjacent to the position of receiver M to improve the receiver coverage in this area. Finally receiver H in was lost, likely due to a high volume of boat traffic.

Abiotic monitoring

During the first year of the study, bottom water temperature was monitored at four locations within the study site. Three temperature loggers (Vemco 8-bit minilog TR) were attached to the moorings of receivers A, E and L within the Plymouth estuary. These temperature loggers were placed 0.5 meters above the bottom and were programmed to record bottom water temperature every 30 minutes. Another temperature logger placed in the southeastern portion of Plymouth Bay recorded bottom water temperature once every two hours. During the second year of the study, another temperature logger was placed on the mooring of receiver T to record bottom temperature in Plymouth Bay. During the second year of the study, problems arose with some of the temperature loggers. The temperature logger at Station A failed, and no temperature data was available for this site. The battery for the temperature logger at station E did not function

5 from January 1, 2009 through April 17, 2009. Finally, the temperature logger at Station K was not functional over a two week period from May 23, 2009 through June 4, 2009. When available, temperature data at each station was analyzed by calculating the weekly averaged bottom water temperature at each site over the course of the study. A handheld YSI (Model #6600, YSI Inc., Yellow Springs, Ohio) was used to measure water quality parameters periodically throughout the duration of the study. The YSI was lowered vertically from the surface to the benthos, and samples were recorded once per second during the deployment. Samples were taken in four locations during the study; in Duxbury Bay near Clarks Island, in Kingston Bay adjacent to receiver L, in the channel at the mouth of the Plymouth estuary, and in Warren , Plymouth Bay.

Results

First Year of Acoustic Telemetry

In total, 31 of the 47 winter flounder tagged during the first year of the study were detected within the Plymouth estuary, resulting in 16,953 acoustic detections. An individual timeline of detections for each tagged fish is shown in Figure 7. Only six of the 24 flounder tagged in the coastal waters of Plymouth Bay during the first year were later detected within the PDK estuary. Flounder tagged in Plymouth Bay were categorized into three distinct behavioral groups based on their observed behavior; 1) coastal residents, 2) spring immigrants and 3) autumn immigrants. Eighteen of the 24 tagged fish (75%) were characterized as coastal residents, meaning they never entered the Plymouth estuary at any point during the year. Five of the 24 flounder (20.8%) were detected immigrating to the Plymouth estuary in the spring. Finally, two of the 24 (8.3%) flounder tagged Plymouth Bay were observed entering the Plymouth estuary in autumn. It should be noted that one of the tagged individuals immigrated to the Plymouth estuary in both spring and autumn, and was included in both categories. Fish tagged within the Plymouth estuary during May and June of 2008 displayed variable residence times and behavior patterns. Seventeen of the 23 tagged fish emigrated from the Plymouth estuary during the month of June. The emigration of these fish coincided with a sharp increase in water temperature within the estuary (Figure 8). Only one individual remained within the estuary after July 31st, when water temperatures exceeded 15 oC throughout the Plymouth estuary. The distribution of tagged flounder within the Plymouth estuary changed markedly during the course of the study (Figure 9). In April, a small number flounder tagged in Plymouth Bay were detected immigrating to the PDK estuary. Throughout May, flounder tagged inside the estuary displayed residence within Duxbury Bay, although some of the flounder began migrating to the mouth of the estuary. In June, as water temperatures increased, a large number of flounder were detected leaving Duxbury Bay and moving southward to the mouth of the estuary. The majority of tagged fish emigrated from the estuary in June, which was evidenced by the high numbers of fish detected at the mouth of the estuary. During July and August when temperatures reached their seasonal maxima, the vast majority of flounder left the estuary for deeper and cooler coastal waters. Of the flounder that remained, their distribution was limited to the mouth of the PDK estuary, the deepest and coolest area within the estuary.

6 Tagged fish displayed unequal habitat usage within the Plymouth estuary. Overall, the highest percentage of detections occurred in Duxbury Bay at receiver C, and at the mouth of the estuary at receiver J. (Figure 10). Tagged fish displayed little residence in Kingston Bay, and none of the tagged fish were detected in Plymouth Harbor. Tagged fish moving between the Plymouth estuary and Plymouth Bay typically remained in shallower water, as noted by the high percentage of detections at receiver J.

Second Year of Acoustic Telemetry

Thus far, 22 of the 25 fish tagged in Plymouth Bay during the second year of the experiment have been detected, yielding a total of 102,662 detections. A daily timeline of detections histories for each fish is shown in Figure 11. Based on their observed movement patterns, tagged individuals were classified into two categories; coastal residents or estuarine users. Coastal residents were fish that were only detected at the outer gate of receivers between Plymouth Bay and Cape Cod Bay. Estuarine users were classified as fish that were detected at the mouth or upper reaches of the Plymouth estuary. Only nine of the 25 (36%) fish tagged in Plymouth Bay were classified as estuarine users. Of the nine fish, only two (tags 2205 and 2206) were detected within the upper reaches of the Plymouth estuary. Thirteen of the 25 (52%) fish were classified as coastal residents. Thus far, three of the 25 tagged fish have not been detected in the study. Two of these fish (tags 2191 and 2200) were released slightly east of the outer receiver gate (Figure 5) and it appears that these fish remained in the waters of Cape Cod Bay. Another fish (tag 2193) was released in Plymouth Bay on 12/30/08 and has not been detected thus far. The fate of this fish is unknown. It may have been captured and not reported, died after tagging, or remained in Plymouth Bay without being detected by a receiver. Eight females released on May 8th, 2009 were visibly gravid and very close to spawning. Of these eight fish, two (tags 2192 and 2206) rapidly moved to the mouth of the Plymouth estuary within ten days of release. It is possible that these fish migrated to the mouth of the estuary to spawn. However, it is clear that six of these nine fish remained in coastal waters to spawn. The distribution of tagged individuals shifted noticeably between March and July of 2009 (Figure 11). In March, relatively few fish were detected either at the mouth of the estuary, or at the outer gate of receivers. This suggests that most tagged fish remained within Plymouth Bay at this time. In April, a proportion of fish were detected at the mouth of the Plymouth estuary, and one fish was detected within the upper reaches of the estuary. During April and May, the majority of fish are detected at the outer receiver gate, indicating that flounder were moving between Plymouth Bay and Cape Cod Bay. In June, a small number of fish were detected at the mouth of the estuary, but again, the majority of fish were detected at the outer receiver gate. Finally, in July, only one fish was detected in the mouth of the Plymouth estuary. During July, the majority of fish were detected at the outer receiver gate, which indicates that tagged fish were remaining in coastal waters during this time.

7 Tagged fish exhibited variable patterns of habitat use within Plymouth Bay and the Plymouth estuary (Figure 12). During the second year of the study, fish displayed low use of the habitats within the reaches of the Plymouth estuary. Nearly half of the total detections occurred at the mouth of the Plymouth estuary. In particular, two tagged fish (tags 2187 and 2197) remained in close proximity to receivers K and G for nearly a month each, resulting in a large number of detections at both receivers. Tag 2187 remained near receivers G and K from March 20th through April 18th, which suggests this fish may have spawned at the mouth of the estuary. A large number of detections were logged at the outer receiver gate, indicating that there was frequent movement of tagged fish between Cape Cod Bay and Plymouth Bay, as well as a high degree of coastal habitat usage.

Abiotic Monitoring

Vertical profiles sampled using the YSI indicated that the Plymouth estuary remained well mixed throughout the study duration. This high degree of mixing is likely due to the interaction between the strong tidal current and the shallow bathymetry of the estuary. Observed salinity values were typically lowest during the spring months and highest during the summer. Salinity was relatively constant at each of the sites throughout the duration of the study. Salinity was the most variable in Kingston Bay, where salinity values ranged from 29 to 33. In contrast, Duxbury Bay had the most stable salinity values, and observations ranged from 30 to 31. Seasonal trends in water temperature were noted for 2008 (Figure 14). Lowest bottom temperatures were observed at each site during the end of January. Temperature increased steadily throughout the spring, and early summer. Over the month of June, water temperatures increased rapidly, and exceeded 15oC throughout the PDK estuary by the end of the month. During August water temperatures at three of the four sites has increased to their seasonal maxima. Bottom temperature was most variable in Duxbury Bay (receiver A), which was the shallowest observed site (mean depth = 4.9m). The coolest summer temperatures were observed in Plymouth Bay, where weekly averaged temperatures exceeded 15oC only twice during the course of the study. In 2009, the lowest temperatures are observed in January and February, and the water temperature gradually increased from March through the summer months (Figure 15). Peak temperatures were observed in July at all three of the observed sites. Bottom temperatures had exceeded 15oC in Kingston Bay (station E) by June 12th and at the mouth of the estuary (Station K) by June 26th. Bottom water temperature never exceeded 15oC in the deeper waters of Plymouth Bay (station T) during the summer months.

Discussion

Our observations support the hypothesis that winter flounder spawning in the Gulf of Maine is not restricted to estuaries. Only 12 of the 49 flounder tagged in Plymouth Bay between 2007 and 2009 were later detected within the Plymouth estuary during the peak spawning season (March-May). Furthermore, twelve flounder were identified as gravid females at the time of release in Plymouth Bay. Only three of these gravid fish were later detected within the estuary. Two of these fish were detected at the mouth of

8 the estuary within ten days of release, and may have moved to the mouth of the estuary to spawn. The third gravid fish was released in November, 2007 and was not detected inside the estuary until May 18th the following year, suggesting that this individual migrated to the estuary for feeding, rather than spawning. In addition, none of the flounder captured inside of the Plymouth estuary appeared to be in spawning condition. Ichthyoplankton sampling has been conducted in the waters of Plymouth Bay since the 1970’s to assess the impacts of the Pilgrim Nuclear Power Station (PNPS). These studies provide valuable information about the spawning patterns of the local flounder population, and offer evidence for spawning in both the coastal water of Plymouth Bay, and within the Plymouth estuary (Chau and Pearce, 1977; Marine Research Inc., 1986). Our results are in agreement previous studies, and suggest that some level of spawning occurs in the coastal waters of Plymouth Bay. The presence of coastal spawning contingents may have an impact on the population dynamics of the Gulf of Maine stock. Divergent spawning migrations may increase the spatiotemporal spread of eggs and larvae, decreasing the likelihood of a failed recruitment event (Lambert, 1990). Winter flounder spawn demersal eggs, which are subjected to a number of anthropogenic activities such as dredging (Pereira et. al., 1999), pollution (Black et al., 1988; Perry et al., 1991) and elevated temperatures (Keller and Klein-MacPhee, 2000). Eggs spawned in estuarine habitats, rather than coastal waters, may be more susceptible to all of these human activities. Estuaries are relatively small in size and have relatively shallow waters, making them more susceptible to fluctuations in water temperature than coastal habitats (Abood and Metzger, 1996). Increases in water temperature have been shown to dramatically decrease the survival of winter flounder eggs (Keller and Klein-MacPhee, 2000). If global warming trends persist and estuarine temperatures rise during the spawning season, the productivity of estuarine habitats may diminish over time due to decreased survival of eggs. Contingents spawning in coastal waters where temperatures are more stable and anthropogenic impacts are less severe may spawn eggs with higher survival rates. Under these circumstances, coastal spawning contingents may stabilize the productivity of the Gulf of Maine stock. Coastal spawning contingents may also increase the level of connectivity that exists between regional populations. Estuarine hydrodynamics (Crawford and Carey, 1985; Chant et al., 2000) and larval behavior (Pearcy, 1962) are thought to promote the retention of larvae within estuaries. Additionally, winter flounder display a high degree of natal homing to estuarine spawning sites (Saila, 1961). These characteristics likely limit gene flow between local populations, giving rise to Perlmutter’s (1947) observation that “the flounder population is comprised of many relatively independent, localized stocks inhabiting the bays and estuaries along the .” The fate of coastal spawned winter flounder larvae has not been studied thus far. Contingents spawning in coastal waters may lead to the dispersal, rather than the retention of larvae. If coastal spawning groups promote larval dispersal, they may provide a subsidy of larvae to estuarine populations. In this case, a single coastal spawning contingent may act as a source population, providing larvae to multiple estuarine populations. On the other hand, these larvae may remain in coastal waters. Whether coastal areas can function as a nursery for winter flounder is currently unknown, because nearly all studies have focused in estuarine, rather than coastal habitats. In the

9 next phase of our research we plan to utilize a coupled biophysical model to examine the development and transport of larvae spawned on the coastal waters in the Gulf of Maine. Further studies need to be done to estimate the extent of coastal spawning in the Gulf of Maine. If coastal spawning groups are more common that previously believed, management measures should be enacted to protect these contingents, and their habitats. During the spawning season, coastal spawning contingents will be more susceptible to commercial harvesting than flounder spawning in estuaries. Temporary fishery closures may be needed to limit the harvest of coastal spawning winter flounder. In addition, current Essential Fish Habitat designations may need to be updated to include coastal habitats as spawning and nursery grounds.

10 References

Able, K.W., 2005. A re-examination of fish estuarine dependence: Evidence for connectivity between estuarine and ocean habitats. Estuarine, Coastal and Shelf Science 64, 5-17. Able, K.W., Fahay, M.P., 1998. The First Year in the Life of Estuarine Fishes in the Middle Atlantic Bight. Rutgers University Press, New Brunswick, NJ, 342 pp. Abood, K.A., Metzger, S.G., 1996. Comparing impacts to shallow-water habitats through time and space. Estuaries 19 (2A), 220-228. Bigelow, H.B., Schroeder, W.C., 1953. Fishes of the Gulf of Maine. U.S. Fish and Wildlife Service, Fishery Bulletin: 53. 577pp. Black, D.E., Phelps, D.K., Lapan, R.L., 1988. The effect of inherited contamination on egg and larval winter flounder, Pseudopleuronectes americanus. Marine Environmental Research 25, 45-62. Chant, R.J., Curran, M.C., Able, K.W., Glenn, S.M., 2000. Delivery of winter flounder (Pseudopleuronectes americanus) larvae to settlement habitats in near tidal inlets. Estuarine, Coastal and Shelf Science 51, 529-541. Chau, T.S., Pearce, B. R., 1977. Real time simulation of the winter flounder larvae entrainment near pilgrim nuclear power station. In: Marine ecology studies related to the operation of the Pilgrim Nuclear Station. Semi-annual report no. 10. Boston Edison Company. Crawford R.E., Carey, C.G., 1985. Retention of winter flounder larvae within a Rhode Island salt pond. Estuaries 8, 217-227. DeCelles, G.R., Cadrin, S.X., 2007. An interdisciplinary assessment of winter flounder stock structure. International Council for the Exploration of the Sea C.M. 2007/L:18, Copenhagen. Greer Walker, M., Harden Jones, F. R., Arnold, G. P., 1978. The movements of plaice (Pleuronectes platessa L.) tracked in the open sea. ICES Journal of Marine Science 38 (1), 58-86. Greer Walker, M., Riley, J.D., Emerson, L.S., 1980. On the movements of sole (Solea solea) and dogfish (Scyliorhinus canicula) tracked off the East Anglican coast. Netherlands Journal of Sea Research 14, 66-77. Heupel, M. R., Semmens, J. M., Hobday, A. J., 2006. Automated acoustic tracking of aquatic animals: scales, design and deployment of listening station arrays. Marine and Freshwater Research 57, 1-13. Hoffman, W.S., Correia, S.J., Pierce, D.E., 2007. Industry Based Survey for Gulf of Maine Cod Pilot Study. Massachusetts Division of Marine Fisheries. 51pp. unpublished. Howe, A.B., Coates, P.G., 1975. Winter flounder movements, growth and mortality off Massachusetts. Transactions of the American Fisheries Society 104, 13-29. Iwanowicz, H. R., Anderson, R. D., Ketschke, B. A., 1974. A study of the marine resources of Plymouth, Kingston and Duxbury Bay. Department of Marine Fisheries. Monograph Series. Number 17. 37 pp. unpublished report. Keller, A.A., Klein-MacPhee, G., 2000. Impact of elevated temperature on the growth, survival and trophic dynamics of winter flounder larvae: a mesocosm study. Canadian Journal of Fisheries and Aquatic Sciences 57 (12), 2382-2392.

11 Kerr, L.A., Cadrin, S.X., Secor, D.H. 2009. The role of spatial dynamics on the stability, resilience and productivity of fish populations: an example based on white perch in the Chesapeake Bay. Ecological Applications (in press). Lambert, T.C., 1990. The effect of population structure on the recruitment of herring. Journal du conseil pour l’Exploration de la mer 47, 249-255. Lawton, R. P., Anderson, R. D., Brady, P., Sheehan, C., Sides, W., Kouloheras, E., Borgatti, M., and Malkoski, V., 1984. Fishes of the inshore Cape Cod Bay: Studies in the vicinity of the Rocky Point shoreline. Observations on the ecology and biology of western cape Cod Bay, Massachusetts. Davis, J. D. and Merriman, D. Springer and Verlag. 11, 191-230. Lux, F.E., Kelly, G.F., 1982. Ichthyoplankton studies of Cape Cod and Massachusetts Bays, 1976-1977. Laboratory Reference Document 81-43. 14pp. Marine Research Inc., 1986. Winter flounder early life history studies related to the operation of Pilgrim Station- A review 1975-1984. 104pp. unpublished. Metcalfe, J.D., 2006. Fish population structuring in the North Sea: understanding processes and mechanisms from studies of movements of adults. Journal of Fish Biology 69 (Supplement C), 48-65. Normandeau Associates, 2001. Ichthyoplankton entrainment monitoring at Pilgrim Nuclear Station, January- December, 2000. In: Marine Ecology Studies Related to Operation of Pilgrim Station. Report no. 57. Pearcy, W.G., 1962. Ecology of an estuarine population of winter flounder, Pseudopleuronectes americanus (Walbaum). Parts I-IV. Bulletin of the Bingham Oceanographic Collection 18, 1-78. Pereira, J.J., Goldberg, R., Clark, P., Perry, D., 1994. Utilization of the Quinnipiac River and New Haven Harbor by winter flounder (Pleuronectes americanus) as a spawning area. New Haven Foundation. Final report. Pereira, J.J., Goldberg, R., Ziskowski, J.J., Berrien, P.L., Morse, W.W., Johnson, D.L., 1999. Essential Fish Habitat source document: Winter flounder, Pseudopleuronectes americanus, life history and habitat characteristics. NOAA Technical Memorandum NMFS NE 138. 39pp. Perlmutter, A., 1947. The blackback flounder and its fishery in New England and New York. Bulletin of the Bingham Oceanographic Collection 11, 1- 92. Perry, D.M., Hughes, J.B., Hebert, A.T., 1991. Sublethal abnormalities in embryos of winter flounder, Pseudopleuronectes americanus, from Long Island . Estuaries 14 (3), 306-317. Powell, J.C., 1989. Winter flounder tagging study 1986-1988 with comments on movements. Rhode Island Division of Fish and Wildlife. 19pp. unpublished report. Sackett, D. K., Able, K. W., Grotheus, T. M., 2007. Dynamics of summer flounder, Paralicthys dentatus, seasonal migration based on ultrasonic telemetry. Estuarine, Coastal and Shelf Science 74, 119-130. Saila, S.B., 1961 A study of winter flounder movements. Limnology and Oceanography 6, 292-298. Secor, D.H., 1999. Specifying divergent migration in the concept of stock: the contingent hypothesis. Fisheries Research 43, 13-34.

12

Figure 1. Distribution of adult (>27cm) winter flounder sampled on the Massachusetts Division of Marine Fisheries Industry Based Survey during March and April of 2004, 2005 and 2007 (from Bill Hoffman, personal communication).

13

Figure 2. Plymouth Bay and the Plymouth estuary in the southern Gulf of Maine.

70°42'W 70°40'W 70°38'W 70°36'W

42°4'N Back µ River Cape Cod Bay Duxbury 42°2'N Bay

Clarks Island

Gurnet 42°0'N Kingston Point Bay Jones "Cowyard" Saquish River Head

Plymouth Bay

P l y m 41°58'N Plymo o u t Harbor h u B th e a c Maine h Rocky Point New Hampshire Gulf of Maine Massachsuetts

RI 0241 Kilometers 41°56'N

14 Figure 3. Length frequency of tagged winter flounder.

8

7

6

5

4

3 # of Tagged Fish Tagged of # 2

1

0 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Length (cm)

Figure 4. Release dates and locations of the 47 winter flounder tagged during the first year of the study. The locations of the 15 acoustic receivers are shown with labels (A-O).

70°42'W 70°40'W 70°38'W 70°36'W 70°34'W

42°4'N Tag Releases

" 30-Nov-07 [ 24-May-08 µ # 6-Jun-08 _ 9-Jun-08 (A X 16-Jun-08 [

42°2'N

(D (B _# X (C

(L 42°0'N (E

(F (G (J (K (N (M (O (I (H

41°58'N

"

41°56'N 0241 Kilometers

15

Figure 5. Release dates and locations of the 25 winter flounder tagged during the second year of the study. The 30 acoustic receivers deployed in the second year of the study are shown with labels (A-DD).

70°42'W 70°40'W 70°38'W 70°36'W 70°34'W

42°4'N Tag Releases [ 10-Dec-08 Y 30-Dec-08 [ 10-Mar-09 µ AA (! " 9-Apr-09 BB (!A (! # 8-May-09

42°2'N

(!D (!B

(!C

(!CC (!L 42°0'N (!E (!P DD(! (!Q (!F (!G (!J (!K (!N (!R (!M (!O (!S (!I (!T (!H " (!U (!V 41°58'N W (!Z (! # (!X [ (!Y [ Y

41°56'N 0241 Kilometers

Figure 6. Latex tubing harness that was developed to externally attach acoustic tags to winter flounder.

16

Figure 7. Daily timeline of detections for each of the fish tagged in the first year of the study. A red box denotes a detection at the mouth of the estuary, and a black box denotes a detection inside the estuary. Fish that were never detected are marked with an asterisk (*). Batches correspond to release dates: 1 = 30-Nov-2007, 2 = 14-May-2008, 3 = 6-Jun- 2008, 4 = 10-Jun-2008 and 5 = 16-Jun-2008. June May April March February January

* * * * * * * * * * * * * * * * * * * * Batch 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 4 4 5 5 5 ID Tag 2052 2059 2069 2072 2081 2087 2050 2051 2058 2062 2063 2065 2071 2076 2077 2084 2091 2096 2053 2064 2074 2082 2092 2089 2094 2054 2090 2055 2056 2057 2060 2066 2067 2068 2070 2075 2078 2079 2080 2083 2085 2086 2088 2093 2095 2073 2061

17

Figure 7 continued. December November October September August y Jul ID # 2052 2055 2056 2057 2059 2060 2066 2067 2068 2069 2070 2072 2075 2078 2079 2080 2081 2083 2085 2086 2087 2088 2093 2095 2050 2051 2058 2062 2063 2065 2071 2073 2076 2077 2084 2091 2096 2053 2064 2074 2082 2092 2089 2094 2054 2061 2090

18

Figure 8. Weekly averaged bottom water temperature at the mouth of the PDK estuary and the number of tagged fish that were detected leaving the estuary each week.

22 10 # of Fish 9 20 Temperature 8 18 7 16 6 5 14 4 3 Temperature (C) Temperature 12 2 10 1 8 0 # of Fish Leaving Detected the Estuary th th 12th 7 29th n 4th l 17th 31st u n u ul J u un 19th un 26th -Jul 3rd Jul 10 May J th - Aug th- - 7 h- t 0 3th- J 0th 4t l 11th- J l 18th- Jul 24th 25th- J 23rd- un 5th- J Jun 2 Jul u u ul ay 3 J J J J Aug 1s ay M Jun 1 Jun 2 Aug 8th- Aug 14th M

19

Figure 9. The number of fish detected monthly at each receiver from April-September of 2008. In April, 23 tagged fish were at large. In May there were 23 tagged fish at large and from June-September there were 47 tagged fish at large.

20

Figure 10. The relative percentage of detections at each receiver during the first year of the study.

21 Figure 11. Daily detection timeline for each of the fish tagged in the second year of the study. A black box indicates a fish detected in the upper reaches of the estuary. A red box denotes a detection at the mouth of the estuary, and a blue box denotes a detection at the receiver gate between Plymouth Bay and Cape Cod Bay. Fish that were not detected are denoted with an asterisk (*). Batch numbers correspond to release dates; 1 = 10-Dec- 2008, 2 = 30-Dec-2008, 3 = 10-Mar-2009, 4 = 9-Apr-2009 and 5 = 8-May-2009.

y Jul June y Ma April March February January

* * * Batch 1 1 1 1 1 1 1 1 1 1 1 2 3 3 4 4 4 5 5 5 5 5 5 5 5 Tag Tag ID # 2204 2186 2208 2198 2197 2199 2195 2202 2187 2188 2205 2190 2207 2201 2193 2203 2196 2194 2185 2191 2192 2206 2200 2184 2189

22

Figure 12. The number of tagged fish detected at each receiver from March-July of 2009. In March, 14 tagged fish were at large. In April, 17 tagged fish were at large and in May 25 tagged fish were at large.

70°42'W 70°40'W 70°38'W 70°36'W 70°34'W 70°42'W 70°40'W 70°38'W 70°36'W 70°34'W

42°4'N # of Fish Detected 42°4'N # of Fish Detected March April

!( 0 !( 0 !( 1 !( 1

µ !( µ !( !( 2 !( (! 4 !( !( !( !( 3

(! 4 42°2'N 42°2'N

!( !( !( !(

!( !(

!( !( !( !( 42°0'N 42°0'N !( !(

!( !( !( (! !( !( !( !(

!( !( !( (! (! (! !( !( (! (! !( !( !( !( !( !( 41°58'N 41°58'N !( !( !( (! !( (!

41°56'N 0241 41°56'N 0241 Kilometers Kilometers

70°42'W 70°40'W 70°38'W 70°36'W 70°34'W 70°42'W 70°40'W 70°38'W 70°36'W 70°34'W

42°4'N # of Fish Detected 42°4'N # of Fish Detected May June

!( 0 !( 0 !( 1-3 !( 1

µ !( µ !( !( 4-6 (! 2 !( !( !( !( (! 7-9 (! 3

(! >9 !( 7 42°2'N 42°2'N

!( !( !( !(

!( !(

!( !( !( !( 42°0'N 42°0'N !( !(

!( !( !( !( !( !( !( !( !( !( (! (! (! !( !( !( (! !( (! !( (! (! (! (! 41°58'N 41°58'N ! !( (! !( ( (! (!

41°56'N 0241 41°56'N 0241 Kilometers Kilometers

70°42'W 70°40'W 70°38'W 70°36'W 70°34'W

42°4'N # of Fish Detected July

!( 0 (! 1

µ !( !( 2 !( !( (! 4

42°2'N

!( !(

!(

!( !( 42°0'N !(

!( (! !( !(

!( (! !(

!( (! !( !( !( 41°58'N

!( !( (!

41°56'N 0241 Kilometers

23 Figure 13. The relative percentage of detections at each receiver during the second year of the study.

70°42'W 70°40'W 70°38'W 70°36'W 70°34'W

42°4'N % of Detections 2nd Year

!( 0 (! <1%

µ !( !( 1-5% !( !( (! 5-10%

(! >20% 42°2'N

!( (!

(!

!( !( 42°0'N (!

!( (! !( (! (! !( !( (! !( !( !( (! 41°58'N !( !( (!

41°56'N 0241 Kilometers

24 Figure 14. Weekly averaged bottom water temperature at four locations within the study site over 2008.

25 Duxbury Bay Kingston Bay 20 Channel Plymouth Bay

15

10

5

0

t h h t h h t d h h h h h t t h d h h d h t t h h h d h h h h r t s t t t t t t t r t s t t t r t t t t s 7 1 0 4 8 n 9 3 7 1 4 8 9 3 6 8 1 3 4 8 3 7 1 2 4 1 5 0 4 1 3 2 1 l 1 3 1 2 1 2 t 2 2 1 1 2 1 2 y 2 n v c n n r r u l l t c t a n n r r a u n g g t o v e c a b b p p y J u u u p p O c J a a e e a a M J u - J u N o D e J J A A a J e e - O - J F M - J h - A A - N - D - - F M - - - M t - S S d t h - - - - - d h - h - - - - h - h t h h h - t 7 h t - - r h s t t h t h d h t t t n h t h d h h 8 t t t s h 0 t 2 5 t h h 3 t 1 t 8 t 6 5 4 8 2 t 1 n t t t 7 2 2 1 8 n 7 1 3 3 1 2 8 3 4 2 2 1 2 2 r 1 6 n 2 5 9 c 1 r 2 y y 1 l l 2 t 1 1 c c b 2 p r 1 u g t 1 t v e n n a r a a u u O c c e e A p n J u g p t c v o a a b a M y u J J O e D D J F e M A a M A u e p O o N J M J D F A S e N M S

Figure 15. Weekly averaged bottom water temperature at three sites during the second year of the study.

20 Station T 15 Station K Station E

10

5

0

t h h h h h h h h h h d h h d h t s t t t t t t t t t t t r t 8 1 7 7 0 4 n 9 5 0 3 3 8 4 3 7 1 1 3 1 2 1 2 1 2 2 1 l 1 n y 2 n c a b r r r r n u l n n b a a u J e J a a e a p p y u - u e J J - J J F M A A M a J h D F M - - - h ------M - t t - t - t d h 7 h h h d h h h h - t h t t 6 t r t s t s t t n 0 t 2 2 4 8 h 1 2 9 3 7 1 7 1 2 t 3 3 1 2 2 1 6 1 n 1 c n 2 r r y y l b r p r 1 u c e a n e b a a a n J u e a A p y e D J a F M M M u J D J F M A a J M

25 Table 1. Timeline of failed attempts to capture adult winter flounder in the PDK Estuary.

Date Gear Location 30-Nov-07 Skiff Trawl Cowyard 3-Mar-08 Skiff Trawl Cowyard and Duxbury Bay 12-Mar-08 Hook and Line Kingston Bay 3-Apr-08 Hook and Line Kingston Bay 10-Apr-08 Hook and Line Duxbury Bay 16-Apr-08 Hook and Line Plymouth Harbor and Kingston Bay 19-Apr-08 Skiff Trawl Duxbury Bay 24-Apr-08 Hook and Line Duxbury Bay 25-Apr-08 Hook and Line Cowyard 2-May-08 Hook and Line Duxbury Bay 21-May-08 Hook and Line Kingston and Duxbury Bay 30-May-08 Hook and Line Duxbury Bay 3-Jun-08 Hook and Line Duxbury Bay 11-Jun-08 Hook and Line Duxbury Bay

26