Incorporating industry based dredge surveys into the assessment of sea scallops, Placopecten magellanicus

Cooperative research utilizing industry vessels represents a viable approach to acquire the data necessary to meet the increasing needs associated with the modern management of marine resources. This dissertation addresses a variety of topics associated with the integration of commercial vessels into the stock assessment of the sea scallop, Placopecten magellanicus. In this study we evaluate the efficacy of utilizing industry vessels with respect to topics that range from rotational closed area survey design, sampling gear evaluation as well as an experiment that broadens the scale of the traditional use of industry vessels in this fishery and provides data to support the use of commercial vessels for surveying sea scallops resource wide. The first paper presents a methodology to evaluate candidate sampling designs for closed area surveys. We simulated scallop populations within a closed area based upon both empirical data and an analysis of the autocorrelation structure of the scallops in that area. From the simulated realizations of the scallop abundance and distribution, three different sampling designs at three levels of sampling were evaluated with respect to bias and accuracy of both mean abundance and variance of the sample mean. The second and third papers take advantage of the ability of commercial vessels to simultaneously tow two dredges. Based on this ability, in the second paper, we estimate the size selectivity of the currently mandated New Bedford Style sea scallop dredge. In addition to estimating the size selective characteristics of this piece of gear, we also estimate the efficiency of the dredge. Both measures are important with respect to correctly estimating the exploitable biomass of sea scallops in rotational sea scallop closed areas. The third paper again used paired data to evaluate the relative changes in the performance of the NMFS sea scallop survey dredge. We utilize a Generalized Linear Mixed Modeling (GLMM) approach to analyzing these data with the goal of characterizing any structural changes in the performance of the dredge that is used to survey both specifically scallop closed areas as well as the entire resource via the annual NMFS time series since the 1970\u27s. The final paper broadens the scale of the utilization of industry vessels and calibrates two of these platforms to the NMFS annual sea scallop survey. We evaluated four separate vessel gear combinations relative to the R/V Albatross IV, throughout the range of the U.S. sea scallop resource and present information to either utilize these vessels to conduct the survey, or at least form a link to a future platform. The results in this dissertation demonstrate that industry vessels represent a feasible option for the collection of sea scallop stock assessment information and present both methods and current information to facilitate their use. These approaches are especially applicable for sea scallops, where the management for this species embraces the spatial characteristics of the underlying population and crafts appropriate management strategies

Results for the 2020 VIMS Industry Cooperative Surveys of the Mid-Atlantic, Nantucket Lightship, Great South Channel, Closed Area I, and Closed Area II Resource Areas

The Virginia Institute of Marine Science (VIMS) conducted high resolution sea scallop dredge surveys of the entire Mid-Atlantic (MAB), the Nantucket Lightship (NLCA), Great South Channel (GSC), Closed Area I (CAI), and Closed Area II (CAII) during July–September 2020. These surveys were funded by the Sea Scallop Research Set-Aside Program (RSA). Exploitable biomass for each survey is shown in Table 1 for each spatially explicit SAMS Area (Scallop Area Management Simulator). SAMS Areas represent management relevant spatial subunits of the resource and explicitly account for differences in recruitment, vital rates, and fishing effort in the forward projection of survey information. Maps of SAMS Areas are provided in Figures 1-5. At the time of the surveys, exploitable biomass estimated from the commercial dredge was 7,443 mt or 16.4 million pounds for the ET Open SAMS Area and 3,081 mt or 6.8 million pounds in the ET Flex SAMS Area. For open bottom in the LI SAMS Area, exploitable biomass was estimated at 6,082 mt or 13.4 million pounds. In the NLCA South Deep SAMS Area, the exploitable biomass was 4,222 mt or 9.3 million pounds. This estimate is lower than total biomass in the SAMS Area and a function of accounting for potential high grading due to scallop sizes observed in this SAMS Area. In the GSC, no data are available for the commercial dredge this year

An Assessment of Sea Scallop Abundance and Distribution in Georges Bank Closed Area I and II and Surrounds: Final Report

For the sea scallop, Placopecten magellanicus, the concepts of space and time have emerged as the basis of an effective management tool. The strategy of closing or limiting activities in certain areas for specific lengths of time has gained support as a method to conserve and enhance the scallop resource. In the last decade, rotational area management has provided a mechanism to protect juvenile scallops from fishing mortality by closing areas based upon scallop abundance and observed age distribution. Approximately half of the sea scallop industry’s current annual landings are attributed to from areas under this rotational harvest strategy. While this represents a management success, it also highlights the extent to which landings are dependent on the effective implementation of this strategy. The continued prosperity of scallop spatial management is dependent on both periodic and large incoming year classes, as well as a mechanism to delineate the scale of a recruitment event and subsequently monitor the growth and abundance of these scallops over time. Current and accurate information related to the abundance and distribution of adult and juvenile scallops is essential for managers to respond to changes in resource subunits

An Assessment of Sea Scallop Abundance and Distribution in the Nantucket Lightship Closed Area and Surrounds - Final Report

For the sea scallop, Placopecten magellanicus, the concepts of space and time have emerged as the basis of an effective management tool. The strategy of closing or limiting activities in certain areas for specific lengths of time has gained support as a method to conserve and enhance the scallop resource. In the last decade, rotational area management has provided a mechanism to protect juvenile scallops from fishing mortality by closing areas based upon scallop abundance and observed age distribution. Approximately half of the sea scallop industry’s current annual landings are attributed to from areas under this rotational harvest strategy. While this represents a management success, it also highlights the extent to which landings are dependent on the effective implementation of this strategy. The continued prosperity of scallop spatial management is dependent on both periodic and large incoming year classes, as well as a mechanism to delineate the scale of a recruitment event and subsequently monitor the growth and abundance of these scallops over time. Current and accurate information related to the abundance and distribution of adult and juvenile scallops is essential for managers to respond to changes in resource subunits

Understanding Dredge Performance for a Lined versus Unlined NMFS Sea Scallop Dredge: Final Report

The sea scallop fishery is typically supported by several primary survey methods (i.e., dredge and optical surveys), which provide multiple, spatially explicit biomass estimates on an annual basis. Since 2015, significant divergence in area-specific biomass estimates between the optical and dredge survey methods has been noted. The divergent estimates are associated with areas of high scallop densities within the Nantucket Lightship Access Area (NL) and the Elephant Truck Access Area (ET). In 2018 and 2019, the disparity in biomass estimates between the different survey methods in the ET was reduced, but in the NL, the issue has continued. Evidence suggests gear saturation is occurring for the survey dredge upon the examination of the 2016 and 2017 survey results for these areas of high scallop density (NEFSC, 2018). This effect is currently the main explanation for the difference in biomass estimates between survey methods. While several independent sources of biomass estimates are beneficial for successful management of the resource, divergent area-specific estimates can contribute to uncertainty when setting annual specifications. Understanding all sources of uncertainty in survey dredge gear performance should be investigated to fully comprehend how and why survey dredge estimates differ from optical survey estimates