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1 This article was downloaded by: [College Of the Holy Cross] On: 31 August 2012, At: 11:08 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Reviews in Fisheries Science Publication details, including instructions for authors and subscription information: Stock Definition and Recruitment: Implications for the U.S. Sea Scallop (Placopecten magellanicus) Fishery from 2003 to 2011 Kevin D. E. Stokesbury a a Department of Fisheries Oceanography, School for Marine Science and Technology (SMAST), University of Massachusetts Dartmouth, Massachusetts, USA Version of record first published: 27 Jun 2012 To cite this article: Kevin D. E. Stokesbury (2012): Stock Definition and Recruitment: Implications for the U.S. Sea Scallop (Placopecten magellanicus) Fishery from 2003 to 2011, Reviews in Fisheries Science, 20:3, To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

2 Reviews in Fisheries Science, 20(3): , 2012 Copyright C Taylor and Francis Group, LLC ISSN: print / online DOI: / Stock Definition and Recruitment: Implications for the U.S. Sea Scallop (Placopecten magellanicus) Fishery from 2003 to 2011 KEVIN D. E. STOKESBURY Department of Fisheries Oceanography, School for Marine Science and Technology (SMAST), University of Massachusetts Dartmouth, Massachusetts, USA The United States sea scallop management plan applies fishing mortality in a uniform manner, assigning a single value of instantaneous fishing mortality (F) to the entire resource. Applying a single value of fishing mortality assumes the scallop resource is a single population. Dividing the resource into Georges Bank and Mid-Atlantic Bight reveals that each has been either excessively fished or underutilized based on the present definition of optimum yield. The sea scallop resource was highest in 2003 and has declined by about 50,000 metric tons, entirely from the Mid-Atlantic Bight. Abundance and the corresponding harvest levels will likely continue if the resource is a single population and scallops in the closed areas of Georges Bank populate the entire resource. Abundance and the corresponding harvest levels will likely decline if Georges Bank and the Mid-Atlantic Bight are separate populations in that scallops within these areas have a closed lifecycle. The depletion of the large number of small scallops in the Mid-Atlantic observed in 2003, and poor recruitment from 2009 to 2011, could lead to a rapid reduction in abundance, seriously impacting the fishery that was valued at US$455 million in Keywords INTRODUCTION Georges Bank, Mid-Atlantic Bight, video survey, optimum yield, fishing mortality A population is a group of interbreeding individuals, existing in three dimensions latitude, longitude, and time which are reproductively isolated from other groups (Mayr, 1942; Taylor and Taylor, 1977). In fisheries science, a stock is the part of the population that is under consideration for utilization (Ricker, 1975). Stock identification involves the recognition of self-sustaining components within natural populations because most population models assume homogeneous vital rates (e.g., growth, maturity, and mortality) and a closed lifecycle in which young fish in the group are produced by previous generations from the same group (Cadrin et al., 2005). Address correspondence to Kevin D. E. Stokesbury, Department of Fisheries Oceanography, School for Marine Science and Technology, University of Massachusetts Dartmouth, 200 Mill Road, Suite 325, Fairhaven, MA 02719, USA. kstokesbury@umassd.edu Overfishing and the overfished status are evaluated for the entire U.S. Atlantic sea scallop, Placopecten magellanicus, resource (USA Federal Regulations, 2004; National Marine Fisheries Service Northeast Fisheries Science Center [NMFS], 2010). Georges Bank and the Mid-Atlantic Bight are assessed separately and then combined for management purposes (Hart and Rago, 2006; NMFS, 2010). The fishery is managed under a partial rotational plan with some areas continually open and fished using a days-at-sea effort control, some areas occasionally opened with a specific total allowable catch for both target and by-catch species, and some areas permanently closed (USA Federal Regulations, 2004; Figure 1). A spatial forecasting model is used in an attempt to avoid setting a fishing level that seems sustainable but in fact is not, given area management policy (NMFS, 2010). Spatially specific fishing mortality, growth rates, seasonal variation in meat condition, and long-term closures may cause extreme variations in defining optimum yield (Hart, 2001; Harris and Stokesbury, 2006; Rothschild et al., 2009; Sarro and Stokesbury, 2009; Mott, 2011). The application 154

3 STOCK DEFINITION AND RECRUITMENT 155 Figure 1 The Industry-SMAST video survey of Georges Bank and the Mid Atlantic Bight sea scallop resource surveyed annually from 2003 to The continental shelf-scale survey stations on a 5.6-km 2 grid (represented as a black dot) and the closed areas are outlined. of a single fishing mortality rate results in treating the scallop resource as a single population. The U.S. sea scallop fishery can be treated as a large experiment with the null hypothesis that the resource is a single population and so a single limit of fishing effort is applied to the entire resource. Alternatively, if Georges Bank and the Mid- Atlantic Bight are different populations, treating them as a single unit will lead to excessive fishing in some areas and underutilization in others, as defined by optimum yield. Although the experiment is still underway, the relationship between harvest, exploitable biomass, and recruitment was examined to provide a perspective on this situation. MATERIALS AND METHODS Estimates of scallop densities on Georges Bank and the Mid- Atlantic Bight were collected using a video survey with a centric systematic sampling design from 2003 to 2011 (Figure 1). Stations were positioned on a 5.6 by 5.6 km grid, and a sampling pyramid was lowered to the sea floor four times at each station (Stokesbury, 2002; Stokesbury et al., 2004). The sampling pyramid had two DeepSea multi SeaCam 2050 R underwater video camera mounted vertically at 700 mm and 1,575 mm above the sea floor, which provided quadrats of m 2 and m 2, respectively (these quadrat sizes include a correction factor for edge effect). Density estimates were calculated using the larger quadrat as the sample area per station equaled m 2, which covers the density range of commercial scalloping (Stokesbury, 2002; Stokesbury et al., 2004). The smaller quadrat size was used to estimating recruitment, as it gives the best estimate of small scallops ( 30-mm shell height) (Carey and Stokesbury, 2011; Stokesbury et al., 2011b). The time, depth, number of live and dead scallops, latitude, and longitude were recorded at each station. After each survey, the videotapes were reviewed in the laboratory and a still image of each quadrat was digitized. The shell height (mm) of each scallop was measured in the still image using Image Pro Plus R software.

4 156 K. D. E. STOKESBURY Mean densities and standard errors of scallops were calculated using equations for a two-stage sampling design (Cochran, 1977). The mean of the total sample is where x i = x = n j=1 n i=1 ( xij m ), (1) ( ) xi, (2) n n denotes primary sample units (stations), m denotes elements per primary sample unit (quadrats), x ij is the measured value for element j in primary unit i, x i is the sample mean per element (quadrat) in primary unit i (stations), and x is the mean over the two stages. The standard error of this mean is 1 S.E.( x) = n (s2 ), (3) where n s 2 = ( xi x) 2 /(n 1) is the variance among primary unit (stations) means. According to Cochran (1977, p. 279), this simplified version of the two-stage variance is possible when the sampling fraction n/n is small. This is the case for the video survey, where thousands of m 2 are sampled compared with millions of m 2 in the study area. The absolute number of scallops within a survey area was calculated by multiplying scallop density by the total area surveyed (Stokesbury, 2002). Estimates of scallop meat weight in grams (w) were derived from shell height (SH, mm) frequencies, and mean weighted depth (roughly 60 m on Georges Bank and 54 m in the Mid-Atlantic Bight, varying slightly from year to year with shifts in scallop distribution) collected during each survey and shell height to meat weight regression used in the NOAA National Marine Fisheries Service 45th stock review (NMFS, 2007): w = exp( (2.95 ln(sh)) 0.51 ln(60))) on Georges Bank, w = exp( (3.18 ln(sh)) 0.65 ln(54))) (4) in Mid-Atlantic Bight. The mean meat weight was multiplied by the total number of scallops in the survey area to estimate the total biomass of scallop meats. The 95% confidence limit was derived by multiplying 1.96 to the standard error, recalculating the mean Table 1 Estimated average biomass (meat weight) and 95% confidence limits in metric tons for the total scallop resource on Georges Bank and in the Mid-Atlantic Bight from 2003 to 2011 Georges Bank Mid-Atlantic Bight Resource Year Average ± 95% CL Average ± 95% CL Average ± 95% CL ,075 13, ,581 35, ,656 48, ,428 19,127 78,613 15, ,041 34, ,793 17,199 84,771 19, ,564 36, ,205 18,763 76,338 14, ,543 33, ,197 18,619 78,756 13, ,953 32, ,562 8,105 83,590 16, ,152 24, ,346 15,296 63,596 7, ,942 23, ,944 16,093 62,626 10, ,570 26, ,237 19,429 63,872 8, ,109 27,473 number of scallops m 2, and using that estimate to determine the total biomass. Annual fishery harvest data were obtained from the NMFS NOAA fish statistic site (NMFS/NOAA regional website for the North East; The exploitable biomass was estimated using the selectivity curve, Selectivity curve = exp( (0.09 SH)) /(1 + (exp( (0.09 SH)))), (5) based on experiments conducted with commercial scallop dredges with 102-mm rings on Georges Bank and in the Mid- Atlantic Bight (Yochum and DuPaul, 2008). The selectivity curve was applied to the scallop meat weight estimated for each 5-mm size bin for Georges Bank and the Mid-Atlantic Bight, resulting in an exploitable biomass estimate. Fishing mortality (F) was calculated using Baranov s catch equation recast (Ricker, 1975; Haddon, 2001): where C/B = F/(F + M) (1 (exp (F + M))), (6) C is the catch, B is the exploitable biomass, F is the instantaneous fishing mortality, and M is the instantaneous natural mortality set at 0.1 (Hart and Rago, 2006). RESULTS The sea scallop resource was highest in 2003 at 196,656 metric tons and has declined by about 50,000 metric tons, entirely from the Mid-Atlantic Bight scallop biomass (Table 1). The Georges Bank scallop biomass has remained at about 85,000 metric tons; a decrease in 2008 was quickly replaced in 2009 and 2010 (Table 1).

5 STOCK DEFINITION AND RECRUITMENT 157 Figure 2 Numbers of small sea scallops Placopecten magellanicus (< 75-mm shell height) in the Mid-Atlantic and on Georges Bank observed with the small video camera from 2003 to In the Mid-Atlantic Bight, 76% of the scallops were small (< 75-mm shell height) in 2003, the results of an extremely strong year class. For the remaining years, small scallop abundance was an order of magnitude lower, ranging from relatively weak (17%) in 2009 to relatively strong in 2004 (35.5%) and 2008 (44.1%) (Figure 2). Scallop recruitment was generally spread over large areas in the Mid-Atlantic Bight (Figure 3). The decline in biomass in the Mid-Atlantic began in 2009, as heavy fishing effort was focused in the southern closed areas, depleting the large number of small scallops observed in 2003, which have not been replaced (Table 1 and Figures 2 and 3). The Georges Bank scallop biomass has remained relatively constant; a decrease in biomass in 2008 was restored by relatively strong recruitments of small scallops in 2007 (52.5%), 2008 (49.5%), and 2009 (42.7%) (Table 1 and Figures 2 and 3). The permanently closed areas contained 29.2%, and the rotational access areas contain 33.0%, of the total Georges Bank scallop biomass in Scallop recruitment was patchy on Georges Bank, with the largest events occurring in the Great South Channel, which was open to fishing, and to a lesser extent in the Closed Area II access area, which was harvested in 2006 and 2009 (Figure 3). Comparing the 2008 small scallop distribution to those observed in 2009, 2010, and 2011 emphasizes the difference between a relatively strong, resource wide, recruitment event, and weaker events concentrated in only a few areas on Georges Bank (Figures 2 and 3). The combination of the extremely large number of small scallops in the Mid-Atlantic in 2003, a large amount of Georges Bank scallop biomass in partially and permanently closed areas, and a management strategy that applies a single fishing limit on the entire resource results in excessive fishing in the Mid-Atlantic Bight and an underutilization resource on Georges Bank based on optimum yield (Figure 4). The scallop fishery continues to be defined as not overfished, and overfishing is not occurring because optimum yield, determined by F MSY or its proxy F MAX, has increased over time. From 2003 to 2007, the fishery was managed using an approximately 17% harvest rate (F max of 0.24) based on the yield per recruit equation and an 89-mm ring in the dredge (USA Federal Regulations, 2004; New England Fisheries Management Council [NEFMC], 2010). An increase in F max to 0.29 was proposed due to the ring size increase to 102 mm, but this estimate was poorly defined, as the higher size selectivity created a flat topped yield per recruit curve (NMFS, 2007). Recently, an F MSY = 0.38 was estimated using a stochastic yield model (NMFS, 2010). DISCUSSION The conundrum of large broods being independent of large numbers of spawning adults has challenged fisheries scientists for years (Gordon, 1954). Despite the changing abundance of scallops in the U.S. resource over the past 25 years, there is still no clear evidence of a stock recruitment relationship (Hart and Rago, 2006). In the Bay of Fundy, recruitment spikes seem to come from the smaller spawning stock sizes (Smith and Rago, 2004). Although the output of fertilized scallop eggs may have increased since the late 1990s, recruitment may still be low as seen in 2009, 2010, and Scallop abundance will probably remain constant or increase if the resource is a single population, and the scallops on Georges Bank populate both Georges Bank and the Mid-Atlantic Bight. There is some evidence to support this hypothesis; within the protected areas, the scallops are large, and there is an exponential relationship between size and egg production (McGarvey et al., 1992; Stokesbury, 2002; Stokesbury et al., 2004). Placopecten magellanicus are gonochoristic, releasing vast quantities of gametes into the water column during each spawn for external fertilization (McGarvey et al., 1992). Scallops aggregate on the scale of centimeters, possibly facilitating increased fertilization success (Stokesbury and Himmelman, 1993). Harris (2011)

6 158 K. D. E. STOKESBURY Figure 3 The spatial distribution of small scallops (< 75-mm shell height) on Georges Bank and the Mid Atlantic Bight from: (a) 2003, (b) 2004, (c) 2005, (d) 2006, (e) 2007, (f) 2008, (g) 2009, (h) 2010, and (i) 2011.

7 STOCK DEFINITION AND RECRUITMENT 159 Figure 3 (Continued.)

8 160 K. D. E. STOKESBURY Figure 3 (Continued.)

9 STOCK DEFINITION AND RECRUITMENT 161 Figure 3 (Continued.)

10 162 K. D. E. STOKESBURY Figure 3 examined the spatial distribution of scallops on Georges Bank from 1999 to 2010 and found 13 persistent high-concentration aggregations suggesting lifecycle closure. The closed areas contained 11 of the 13 persistent scallop aggregations. Juvenile (Continued.) scallops were also more crowded on Georges Bank than in any other area, possibly as a result of differences in substrates, starfish interaction, and abundance of filamentous fauna (Carey and Stokesbury, 2011). This resulted in adult distribution that Figure 4 Comparison of the scallop harvest to the estimated exploitable biomass (both are meat weights in metric tons) for Georges Bank ( ) and the Mid-Atlantic Bight ( ) and the entire resource ( ) from 2003 to The estimated optimum yield curves for 2003 to 2007 (F MAX = 0.24), proposed 2008 (F MAX = 0.29), and the 2010 (F MSY = 0.38) are also represented (USA Federal Regulations 2004; NMFS, 2007, 2010). Note: the 2011 harvest estimate is only until December as the data was not available to the end of the fishing year 31 March 2012.

11 STOCK DEFINITION AND RECRUITMENT 163 were slightly more crowded on Georges Bank than in the Mid- Atlantic Bight, suggesting higher fertilization success (Carey and Stokesbury, 2011). Modeling the relationship between scallop density, size, and fertilization rate, Smith and Rago (2004) estimated an increase in fertilized eggs of several orders of magnitude beginning in 1994 on Georges Bank and 1998 in the Mid-Atlantic Bight. Larvae from scallops spawning close to the shelf break southeastern side of Georges Bank could recruit to the Mid-Atlantic Bight due to the persistent along-shelf current (Tian et al., 2009b). Scallop abundance will probably decrease rapidly if Georges Bank and the Mid-Atlantic are separate populations. This hypothesis is supported by modeled scallop larval dispersion, suggesting that high juvenile retention areas on Georges Bank generally overlapped the high concentrations of adult scallops (Tian et al., 2009a,c). Fishing effort is high enough to remove the large scallops, reduce densities, and disperse aggregations, resulting in decreased reproductive output and lower fertilization success. The Georges Bank stock will probably remain at a constant biomass or increase while the Mid-Atlantic Bight would decrease; this pattern seems to be occurring and further supporting this hypothesis (Table 1). The large proportion of the scallop biomass locked in the closed areas will result in continually higher pressure on Georges Bank and the Mid-Atlantic open areas until the populations in these areas are depleted. This situation is exasperated when the total allowable catches for the George Bank access areas are only partially harvested (on average, 1,000 metric tons per closed area to date) due to early closure from bycatch limitations (NMFS/NOAA regional website for the North East; It is possible that the stock recruitment relationship is so unpredictable that present models are unable to capture the dynamics of the system. In this case, the most prudent way to manage the scallop fishery would be to abandon overall fishing effort limits and instead spatially and temporally track strong scallop year class size and abundance, protecting scallops while they are young and intensely harvesting them when they are old before they are lost to senescence, which has occurred in the Georges Bank closed areas (Stokesbury et al., 2007). This management approach would avoid the wasteful situation that occurred in the Mid-Atlantic Bight when 10.4 billion juvenile scallops disappeared between 2003 and 2004, probably due to incidental discard fishing mortality (Stokesbury et al., 2011b; Hart and Shank, 2011; Stokesbury et al., 2011a). The management of sea scallops is a deceptively difficult problem. The fishery has grown from a low of 5,500 metric tons landed in 1998 to an average of 26,000 metric tons from 2003 to 2010, with high prices worth US$455 million in 2010 (NMFS, 2010; Voorhees and Pritchard, 2010). The scallop resource is above 125,000 metric tons the estimated biomass at maximum sustainable yield (NMFS, 2010) (Table 1, Figure 4). Further, with almost 60% of the Georges Bank stock in closed/access areas, there is no biological danger to the species. Therefore, fishermen should be able to harvest the resource with little impairment. If the Mid-Atlantic Bight and Georges Bank are separate populations, the excessive harvests in the Mid-Atlantic and the permanently closed areas on Georges Bank, plus the poor recruitment from 2009 to 2011, could lead to a rapid reduction of abundance and landings given the present management practice. ACKNOWLEDGMENTS Thanks to my students, staff, the owners, Captains and crews who sailed on these fffresearch trips. J Carey created the maps. J Carey, D Georgianna, S Inglis, B Rothschild and M Stokesbury provided insightful comments on the manuscript. Aid was provided by NOAA awards: NA04NMF , NA04NMF , NA05NMF , NA06NMF , NA08NMF , NA09NMF , the sea scallop fishery and supporting industries. The views expressed herein are those of the author and do not necessarily reflect the views of NOAA or any other agencies. REFERENCES Cadrin, S. X., K. D. Friedland, and J. R. Waldman. Stock Identification Methods: Applications in Fishery Science, p Amsterdam: Elsevier Academic Press (2005). Carey, J. D., and K. D. E. Stokesbury. An assessment of juvenile and adult sea scallop, Placopecten magellanicus, distribution in the northwest Atlantic using high-resolution still imagery. J. Shellfish Res., 30: (2011). Cochran, W. G. Sampling Techniques. 3rd Edition, p New York: John Wiley & Sons (1977). Gordon, S. H. The economic theory of a common-property resource: The fishery. J. Pol. Econ., 62: (1954). Haddon, M. Modeling and quantitative methods in fisheries. London: Chapman & Hall, 406 pp (2001). Harris, B. P. Habitat conditions in persistent high-concentration sea scallop (Placopecten magellanicus) aggregations on Georges Bank, USA. Doctorate of Science thesis. University of Massachusetts, Dartmouth, MA, USA (2011). Harris, B. P., and K. D. E. Stokesbury. Shell growth of sea scallops (Placopecten magellanicus Gmelin, 1791) in the southern and northern Great South Channel, USA. ICES J Mar Sci., 63: (2006). Hart, D. R. Individual-based yield per recruit analysis, with an application to the Atlantic sea scallop, Placopecten magellanicus. Can. J. Fish. Aquat. Sci., 58: (2001). Hart, D. R., and P. J. Rago. Long-term dynamics of U.S. Atlantic sea scallop Placopecten magellanicus populations. N.Am.J.Fish. Manag., 26: (2006). Hart, D. R., and B. V. Shank. Mortality of sea scallops Placopecten magellanicus in the Mid-Atlantic Bight: Comment on Stokesbury et al. (2011). Mar. Ecol. Prog. Ser. 443: (2011). Mayr, E. Systematic and the origin of species. New York: Columbia University Press, 315 pp. (1942). McGarvey, R., F. M. Serchuk, and I. A. McLaren. Statistics of reproduction and early life history survival of the Georges Bank sea

12 164 K. D. E. STOKESBURY scallop (Placopecten magellanicus) population. J. Northwest Atl. Fish. Sci., 13: (1992). Mott, C. L. Examining variation in sea scallop shell growth and environmental conditions across Georges Bank and the mid-atlantic. Master of Science Thesis. University of Massachusetts, Dartmouth, MA, USA (2011). National Marine Fisheries Service Northeast Fisheries Science Center (NMFS). Atlantic sea scallop stock assessment for In: 45th Northeast Regional Stock Assessment Workshop (45th SAW) assessment report. US Department of Commerce, Northeast Fisheries Science Center Ref Doc Available from (2007). National Marine Fisheries Service Northeast Fisheries Science Center (NMFS). Atlantic sea scallop stock assessment for In: 50th Northeast Regional Stock Assessment Workshop (50th SAW) assessment report. US Department of Commerce, Northeast Fisheries Science Center Ref Doc Available from publications (2010). New England Fisheries Management Council (NEFMC). Framework Adjustment 21 to the Atlantic Sea Scallop Fisheries Management Plan. Available from (2010). Ricker, W. E. Computation and interpretation of biological statistics of fish populations. Bull. Fish. Res. Bd Can., 191:1 382 (1975). Rothschild, B. J., C. F. Adams, C. L. Sarro, and K. D. E. Stokesbury. Exploration of variability in sea scallop shell height-meat weight relationship. ICES J Mar Sci., 66: (2009). Sarro, C. L., and K. D. E. Stokesbury. Spatial and temporal variation in the shell height/meat weight relationship of the sea scallop (Placopecten magellanicus) in the Georges Bank fishery. J. Shellfish. Res., 28: 1 7 (2009). Smith, S. J., and P. Rago. Biological reference points for sea scallops (Placopecten magellanicus): The benefits and costs of being nearly sessile. Can. J. Fish. Aquat. Sci., 61: (2004). Stokesbury, K. D. E. Estimation of sea scallop, Placopecten magellanicus, abundance in closed areas of Georges Bank. Trans. Am. Fish. Soc., 131: (2002). Stokesbury, K. D. E., J. D. Carey, B. P. Harris, and C. E. O Keefe. Discard mortality played a major role in the loss of 10 billion juvenile scallops in the Mid-Atlantic Bight: Reply to Hart and Shank (2011). Mar. Ecol. Prog. Ser., 443: (2011a). Stokesbury, K. D. E., J. D. Carey, B. P. Harris, and C. E. O Keefe. Incidental fishing mortality may be responsible for the death of ten billion juvenile sea scallops in the Mid Atlantic. Mar. Ecol. Prog. Ser., 425: (2011b). Stokesbury, K. D. E., B. P. Harris, M. C. Marino II, and J. I. Nogueira. Estimation of sea scallop abundance using a video survey in offshore USA waters. J. Shellfish Res., 23: (2004). Stokesbury, K. D. E., B. P. Harris, M. C. Marino II, and J. I. Nogueira. Sea scallop mass mortality in a marine protected area. Mar. Ecol. Prog. Ser., 349: (2007). Stokesbury, K. D. E., and J. H. Himmelman. Spatial distribution of the giant scallop Placopecten magellanicus in unharvested beds in the Baie des Chaleurs, Québec. Mar. Ecol. Prog. Ser., 96: (1993). Taylor, L. R., and R. A. J. Taylor. Aggregation, migration and population mechanics. Nature, 265: (1977). Tian, R. C., C. S. Chen, K. D. E. Stokesbury, B. J. Rothschild, G. Cowles, Q. C. Xu, B. P. Harris, and M. C. Marino II. Dispersal and settlement of sea scallop larvae spawned in the fishery closed areas on Georges Bank. ICES J. Mar. Sci., 66: (2009a). Tian, R. C., C. S. Chen, K. D. E. Stokesbury, B. J. Rothschild, G. Cowles,Q.C.Xu,B.P.Harris,andM.C.MarinoII.Modelingthe connectivity between sea scallop populations in the Middle Atlantic Bight and over Georges Bank. Mar. Ecol. Prog. Ser., 380: (2009b). Tian, R. C., C. S. Chen, K. D. E. Stokesbury, B. J. Rothschild, G. Cowles, Q. C. Xu, B. P. Harris, and M. C. Marino II. Sensitivity analysis of sea scallop (Placopecten magellanicus) larvae trajectories to hydrodynamic model configuration on Georges Bank and adjacent coastal regions. Fish. Ocean., 18: (2009c). USA Federal Regulations. Fisheries of the Northeastern United States: Atlantic Sea Scallop Fishery. Amendment 10, USA Fed Reg 69:38/26 February 2004, 50 CFR Part 648 (2004). Voorhees,D.V.,andE.S.Pritchard.Fisheries of the United States 2010: Fisheries Statistics Division. Silver Spring, MD: NOAA National Marine Fisheries Service (2010). Yochum, N., and W. D. DuPaul. Size-selectivity of the northwest Atlantic sea scallop (Placopecten magellanicus) dredge. J. Shellfish Res., 27: (2008).