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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) Appendix 2 - SABRE Site Review Report Background The South Atlantic Bight Recruitment Experiment (SABRE) was initiated in FY 1991. This site review report fulfills the requirement of the Coastal Fisheries Ecosystem (CFE) theme to conduct such reviews after 3 years of program support. The review was conducted at the Duke University Marine Laboratory, Beaufort, North Carolina, on January 27-28, 1994. The concept of SABRE had been nurtured during the 1980s by NOAA and academic scientists. The advent of the Coastal Ocean Program (COP) provided support that launched SABRE in 1991 as one of two initial projects within CFE. The goal of SABRE is to understand the relationship between variation in environmental factors and the variable recruitment of “estuarine-dependent” fishes in the South Atlantic Bight (COP, 1993). The program addresses NOAA's need to build sustainable fisheries, a major element of the NOAA Strategic Plan (NOAA, 1993). SABRE investigations center on Atlantic menhaden, Brevoortia tyrannus, an abundant and heavily exploited species that is representative of many coastal fishes that are estuarine-dependent in the juvenile stage. Past research has indicated that several factors, including storms, larval advection, and juvenile survival in estuaries all may have important effects on recruitment and year-class strength. The SABRE program addresses many of these factors and examines characteristics of survivors across life history stages. SABRE's approach to investigate recruitment is to study survivors at “critical junctures” in their life history (SABRE, 1994). This approach is an alternative to “traditional” approaches based on estimating mortality rates of early life stages. Process-oriented studies are not emphasized in SABRE, although some are included. Traditional recruitment research, which relies on estimating mortality rates and processes correlated with it, is thought by SABRE to be too complex and too expensive. The approach taken by SABRE depends upon establishing birthdate distributions from otolith-aging analyses and comparing those distributions at several stages during the first year of life. Observed shifts in apparent birthdate distributions result from stage-selective mortalities and can be the basis to judge how changes in habitat or environment affected the generation of recruits. A strength of SABRE is the successful partnership that has been developed between NOAA and academic scientists. The leadership of SABRE is strong and
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) complementary. In this sense, SABRE is an excellent example of how CFE research was envisioned. SABRE is entering its third field season in 1994. Lower than expected budgets have limited offshore sampling, and menhaden eggs and larvae have proven to be elusive. Sampling older larvae at inlets has been far more predictable. A shift in emphasis is evolving in SABRE that focuses increasingly on the late postlarval stages at the inlets and juvenile stages within the estuaries. The panel review team recognized that SABRE was making significant progress in several areas. The following are discussed specifically: (1) offshore processes (eggs and larvae); (2) inshore processes (late-stage larvae and juveniles); (3) physics and physical modeling; (4) biological modeling; and (5) new technologies. Offshore Processes Offshore sampling of limited spatial and temporal extent in 1992 and 1993 found few menhaden eggs and indicated that their distributions were extremely patchy in space and time. An optical particle counter (OPC) has been modified by SABRE scientists to sample menhaden eggs. This new sampler potentially is an important innovation for ichthyoplankton surveys. A large patch of menhaden eggs was discovered and sampled by the OPC during January 1994, demonstrating the promise of this instrument to discover patches and delineate their structure quickly and efficiently. The OPC technology would benefit if supplemented by effective net or acoustic sampling to define both the spatial extent and vertical distribution of eggs and young larvae. The panel subgroup believes that it is important for SABRE to know the temporal and spatial distribution of eggs to initialize the birthdate distribution and provide data to model the inshore drift of larvae. The subgroup concedes that this will require more extensive financial resources than are currently available, given the large expanse of potential spawning area. The subgroup recognized that limited vessel time and scarce funds constrained the offshore sampling effort and that it would be difficult for SABRE to mount an effort greater than that now being undertaken without additional NOAA support. However, use of small nets to survey wide areas (e.g., CalVet nets; Lasker, 1985) may be one means to define and map large areas of menhaden egg occurrence quickly and efficiently. Historical samples of ichthyoplankton [e.g., from the Marine Resources Monitoring, Assessment, and Prediction activity (MARMAP)] may be a source of information on menhaden egg occurrences and distributions which should be explored.
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) SABRE has not emphasized process-oriented research. But, promising studies on larval nutritional condition (metabolic enzyme analyses and RNA/DNA ratios) indicate that larval condition varies. Understanding larval nutrition and how it affects growth or survival could be a valuable product of SABRE research. The plan to examine otoliths from larvae sampled for condition studies to determine their age and estimate growth rates will provide valuable correlative data. A single predation study by SABRE indicated that chaetognaths probably were not a significant predator of menhaden larvae. The offshore egg and larval stages of menhaden extends over the first 50 to 90 days of life. A large fraction of the variability in survival and eventual contribution to variability of year classes could occur during the offshore phase. To meet SABRE's long-term goals it is important for the program to evaluate this source of variability and compare it to that generated during the estuarine juvenile phase. Inshore Processes The SABRE inshore program has several components that address the late larval and juvenile stages. Sampling at the inlets for larvae is a cost-effective means to sample and quantify numbers of larvae that enter the estuary. Physical modeling and moorings addressing near-inlet conditions must be closely tied to biological sampling at inlet mouths. These physical studies, if linked to the offshore physical modeling, could provide an effective tool to assess entry to estuaries. The subgroup believes that inlet sampling should be linked to offshore larval sampling; two approaches to accomplish this could include (1) extensions of presently supported behavioral research on smaller planktonic larvae, to larger larvae which are competent to enter the estuary, and (2) studies of nutritional condition of larvae entering the estuary to relate to condition of larvae offshore. It is possible that changes in behavior of larger larvae may promote retention near shore and prevent offshore, but not alongshore, advection. Behavioral information is important to provide data to help direct physical modeling. In inlet studies, the best temporal information is provided by NMFS surveys at Beaufort Inlet which have yielded time series data crucial to SABRE. The time series indicates that menhaden larval abundances vary on intra- and inter-annual time scales at Pamlico Sound inlets. The relationship between patterns of ingress at Beaufort Inlet and subsequent age 0 + abundance derived from virtual population analysis (VPA) suggested that the offshore larval phase may be important (i.e., annual ingress to estuaries may be
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) related to subsequent catch or year-class strength). As a result, a project to sample larvae at several inlets was developed to quantify ingress to Pamlico Sound. This research component does not appear to be well justified and results may not be critical to SABRE, because the variance of age 0 + abundance estimates will be high and ingress of larvae to a single estuarine system may not be reflected in VPA results that depend upon contributions of age 0 + menhaden from many estuaries. Also, because only one data point per year can be obtained to correlate larval ingress and age 0 + abundance, it will take many years to detect any relationship that might exist. Studies of otoliths from menhaden larvae and juveniles play a central role in SABRE; extracting information from the chronological record in otoliths is consistent with the SABRE philosophy of examining characteristics of survivors. SABRE research has demonstrated that otolith age estimates up to 200 days after hatching are reliable, which allows estimates of birthdate distributions of survivors to be established at different life stages. Future otolith research will require application of improved and new technology. The review team encourages SABRE scientists to examine emerging otolith technologies (including image analysis and elemental analysis) as possible ways to elucidate events in the early life history of survivors. The subgroup was concerned that some SABRE investigators may be confusing birthdate distributions of survivors with temporal distribution of spawning. To date, SABRE has been unable to confirm the latter, but it remains an important goal. With continued sampling at spatially separated inlets, determining variations in the birthdate distributions at these inlets in conjunction with a verifiable model of transport toward inlets may provide an indirect approach to identify offshore spawning areas and times. Studies by SABRE on dispersion of late-stage larval and juvenile menhaden within estuaries are only beginning. Although there was evidence of spatial variability in size and age distributions of estuarine juveniles, the subgroup noted that such results could be a sampling artifact. Improved and more extensive sampling to define the age structure of estuarine juveniles will be required. Although research to date has concentrated on sampling menhaden at inlets and in the estuaries, other estuarine-dependent fishes are also collected, including several species of commercial importance. These collections are an important source of information for future research. Comparisons of temporal and distributional patterns of occurrence among species may be effective to establish mechanisms of transport and estuarine entry. SABRE has justified its expansion of research on estuarine juveniles based on a life-stage model which suggests that significant variation in year class strength is contributed during the estuarine juvenile phase. The subgroup endorses the estuarine
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) emphasis by SABRE in years 4 and 5 but cautions that improved temporal sampling of eggs offshore will be needed if the program continues beyond its fifth year. Physics and Physics Modeling Overall, the efforts by SABRE to quantify the physical mechanisms involved in the life history of menhaden are generally well planned. However, the program shouldalso question the extent to which physical measurements and models are meeting needs of the program. For example, what is the reliability of the finite element model? The remote sensing effort has provided useful background information, but must be focused better in both time and method of application if it is to serve SABRE 's goals. Finally, the moored instrument effort seems poorly integrated with other elements in SABRE and it is unclear how mooring data will be used. The reliability of models and the scope of future modeling efforts should be clarified. Can the finite element model reproduce currents observed in the many past mooring programs conducted in the South Atlantic Bight? Does the model produce Lagrangian statistics comparable to those that will be measured in the drifter program? Precision levels are crucial to decide if the model sufficiently addresses questions posed by the program. With de-emphasis of offshore egg and larval research, the model can be used to gain insight into how transport processes may operate. But, back-calculation of larval drift from the model is fundamentally flawed because calculations cannot track non-reversible processes associated with turbulent dispersion and larval mortality (which isn't included in the model). The modeling, which is promising, should proceed to a verification phase and then to a set of simulations to address, from a conceptual basis, issues that cannot be addressed in the offshore sampling effort because of insufficient funding. The subgroup does not believe that the model by itself is sufficient to replace offshore sampling. The nearshore inlet model is both interesting and relevant, but to date has not been developed for the North Carolina inlets and it appears that this modeling effort will be discontinued. A significant point is that Onslow Bay inlets, which are the subject of SABRE investigations, differ from Chesapeake Bay or river-dominated inlets such as Cape Fear and others to the south. If the goal is to understand physics of inlets, a coupled model including the sounds, inlets, and near-shore shelf in the sampling region should be developed. Such a model also must also be cognizant of and incorporate the known biology of menhaden early life stages to contribute fully to SABRE. The remote sensing analysis seems only loosely tied to other SABRE components. How will Coastal Zone Color Scanner (CZCS) data be used? Will a
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) comparative analysis of sea surface temperature (SST) and biological data be carried out? If so, analytical techniques to compare these data must be developed. Finally, it is not certain that velocity fields can be depicted accurately from the SST data. There are a few successes using this approach to quantify surface circulation, but most attempts have not been tested against sea-truth data. The near-inlet moored instrument program potentially can provide significant contributions to SABRE. However, velocity vector diagrams for the near-inlet regime do not automatically contribute to a description of inlet larval flux. It was unclear how SABRE will use these data. Will they be used to verify the transport models and if so, are the mooring placements appropriate? The program should carefully consider its requirements for physical data to address recruitment variations in the context of the SABRE science plan. Biological Modeling The basic biological model employed to date is derived from a life table approach. It has the merits of allowing detailed resolution of mortality patterns for different life stages. It is constrained by certain assumptions—stable age distribution and equilibrium population dynamics—and may require more than five years to produce definitive results because of probable high levels of interannual variability. This model has indicated that the most sensitive component of the life history is the juvenile stage. That conclusion has led several SABRE investigators to focus new effort on resolving the dynamics of juvenile survivorship by otolith analysis and increased field effort within the estuaries. While that may be wholly justified, caution is required because “sensitivity” evidence is derived in part from the model structure and, therefore, may mislead the research effort. Analysis of life table models often leads to the conclusion that the juvenile stage is where population regulation is most important because numbers are declining exponentially while reproductive value is increasing as its mirror image. Their intersection produces the dynamics perceived as maximum sensitivity at the intermediate (juvenile) life stage. High sensitivity in the juvenile stage may, in fact, be real for menhaden. Alternatively, the apparent sensitivity of juveniles could be a consequence of the model that was applied. We recommend that the modeling approach be expanded. For example: The menhaden catch record in the fishery offers opportunity to analyze interactions of variability among age groups. A time series analysis of the catch record could be used to generate input for the life stage model
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) which might represent the stochasticity of recruitment to earlier life stages and could be the basis for a model and analysis. The planned development of the individual-based model (IBM) might allow SABRE investigators to move beyond the constraints of otolith data by using the IBM to generate variability in size (and age) distributions of recruits to the “peanut” fishery.12 Hindcasting with that model could be the basis for inferring size-dependence of survivorship bottlenecks in the juvenile or larval stages. Following the philosophy of the project, the models should be used to generate alternative hypotheses, then winnowed by comparisons with the data and/or expertise of investigators. Predators and predation rates probably will become an object of research as emphasis on the juvenile stage increases. Accordingly, a non-linear approach to modeling the density dependence of recruitment and/or predator functional responses would help represent possible rapid changes in predation effects. Similarly, intra-seasonal variability in predator-prey interactions might be the justification for a field assessment of the frequency of menhaden in predator diets. It might also be a basis for inferences about local and large-scale migration patterns. At the least, investigators need a means to explore the diversity of likely causes of size-specific mortality. Models can help in this task. Our recommendation is not intended to dissuade SABRE from using the life table approach. It is a valuable tool. However, we are concerned that a single theoretical/analytical focus may lead to a biased and insufficient view of the problem. A broad modeling approach will offer the comfort of confirmation and the prospect of new insights. New Technologies SABRE has adopted, developed, or applied several new or advanced technologies, including remote sensing, finite element modeling, development of an optical egg counter, otolith applications, and biochemical condition indices. There has been excellent progress in developing some technologies. The rapid metabolic enzyme method to define larval menhaden condition is particularly promising as a means to create an index of the probability of starvation in the SABRE sampling area. It is not 12 “Peanuts” are age 0 + menhaden newly recruited to the fall fishery.
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) clear, however, whether enough synoptic biological information will be collected in the offshore area to maximize its potential benefits. The OPC, modified for use as a menhaden egg sampler, is now developed and operational for 1994 cruises, which is a significant step forward for SABRE. Its present mode of deployment restricts inferences because it only samples a single, near-surface depth. The instrument will be very useful to locate egg patches in SABRE and could serve similar purposes in other programs. Without concomitant net sampling to define the areal and depth-integrated abundances of eggs, the OPC may not achieve its full potential in SABRE. A multifrequency, towed, acoustic particle sensor also is being deployed, which, when used with the OPC, will provide a “smart-sampling” capability that could add unique dimensions to ichthyoplankton and zooplankton sampling. The present limitations of the offshore program in SABRE will limit the usefulness of these technologies. Otolith aging studies are state of the art and are essential for SABRE to determine birthdate distributions of survivors. Proven methods are being followed in an attempt to extend use of daily increment technology to menhaden juveniles more than 200 days old. Attempts to undertake elemental analyses in otoliths as a means to interpret environmental conditions in early life histories were not successful, but there is potential to explore these emerging technologies further. Satellite remote sensing, an advanced but not new technology, if used to test the finite element model, might be a useful tool to help interpret larval distributions and transport on the shelf. However, it is not clear that any additional satellite studies are planned in SABRE. Findings and Recommendations The management team and overall management are strong in SABRE and should be maintained. Addition of a physical oceanographer to the Program Management Committee may be desirable. The added emphasis on estuarine studies of juvenile menhaden is endorsed by the subgroup. A caveat is required because little is known about the importance of offshore processes that affect eggs and larvae. There is little likelihood that the offshore component of SABRE can be expanded given present funding levels and level of logistical support. A careful use of existing data sets and models to explore offshore dynamics is recommended as a cost-effective but partial alternative.
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) Juvenile studies are important. The life-table model, although based upon incomplete information about life stages of menhaden, indicates that this stage is sensitive and worthy of critical examination. The subgroup encourages the continued application of the finite element model and the eventual linkage of it to near-inlet transport models, which must be developed. This modeling should be done in conjunction with behavior studies, particularly those that define the vertical distribution behavior of larval menhaden. Observed egg distributions should be used to generate advection pathways for larval menhaden to predict how larvae reach the inlets. The model cannot be used to back-calculate egg distributions. Net collection methods that are rapid and effective should be included in the offshore program as a means to determine the depth-integrated distributions and abundances of menhaden eggs. The CalVet net used in California Current studies of anchovy eggs may be a suitable gear. Historical samples of menhaden eggs and larvae, if they exist, should be obtained and examined. The MARMAP samples that were processed in South Carolina are an example; others may exist. Such samples could help to define spawning areas and the seasonal dynamics of egg production. As juvenile studies are expanded in scope, study of the predation process will become increasingly important. Carefully designed studies of predation on juveniles within the estuaries will be required. Additional biological and biological-physical modeling is encouraged. Individual-based models linked to physical transport models are a promising approach. Box models in which dynamics of offshore stages (eggs and larvae) and inshore stages (juveniles) are highlighted, should be considered. Synthesis documents on menhaden biology and shelf physics of the South Atlantic Bight will be useful. The former should include a critical assessment of estuarine-dependence and the role of nearshore nurseries for menhaden. Such documents apparently were anticipated in SABRE's original plan. They should be produced. The procedures to request proposals, review them, and select projects for support have followed high standards in SABRE. Nevertheless, the procedures that were followed may not always promote the most innovative science. Future calls for proposals should encourage a degree of innovation, in addition to filling critical gaps in the program.
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) Inclusion of other estuarine-dependent species in SABRE, especially if research emphasis moves toward juvenile stages in estuaries, is desirable. Summary The subgroup recommends that COP continue its support of SABRE for the remainder of its planned five-year term. In addition, the subgroup summarizes below its findings regarding SABRE's goals and objectives, accomplishments, utility, responsiveness to past review, and future plans. Goals and Objectives — SABRE's goal is to understand the relationship between variation in environmental factors and the variable recruitment of estuarine-dependent fishes, specifically menhaden, in the South Atlantic Bight. Hypotheses are not explicit in SABRE, but the research embraces a philosophy that advocates an “alternative approach” to recruitment variability research. This approach, which the subgroup supports, relies on detailed investigations of characteristics and birthdate distributions of survivors at several life stages, which will reveal how stage-specific and size-specific processes operated to control the resulting recruitment. In this approach, hypotheses become emergent features of the research. Success will depend on determining birthdate distributions of menhaden at critical egg, larval, and juvenile life stages. Accomplishments — SABRE has demonstrated progress in several areas. Ingress at inlets and patterns of its variability have been defined. Techniques for aging otoliths of menhaden up to 200 days old have been developed. The optical particle counter has been modified and developed to sample menhaden eggs. The application of metabolic enzyme analyses to determine the nutritional condition of menhaden larvae apparently is successful. The finite element model of circulation and probable transport in the South Atlantic Bight is functional and has potential to provide understanding of advective pathways for eggs and larvae. The formation of an effective partnership between NOAA and academic scientists and of a highly effective management team has contributed strongly to the effectiveness of the program. Utility — The research carried out and planned should lead toward better understanding of how recruitment variability is generated in menhaden and will define critical life stages or habitats in the recruitment process. Menhaden ecology may be representative of the ecology of many estuarine-dependent species; thus, findings from SABRE may have wide application in understanding the effects of the environment on estuarine-dependent fishes. New sampling technologies developed for SABRE will be transferable to other fishery oceanography programs. The overall result of the research by SABRE will lead fisheries toward becoming a predictive science.
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) Responsiveness to Earlier Reviews — SABRE apparently uses and is responsive to its Technical Advisory Group. The present review is the program's first formal review; the CFE TAC has not reviewed the program since its initiation. Planning and Management — Many feel that SABRE is the best of COP programs in the sense that an effective partnership has been formed, much of it before COP formally was established, by combined efforts of NOAA and academic scientists. The partnership and team continue to be strong. Research planning is ongoing and has evolved as logistical support proved to be insufficient for a large offshore effort. Some projects have been terminated in favor of new ones more related to the central goals and shifting emphasis of the program. An objective proposal process has been used to bring new projects into the program. Some criticisms of research project design may be warranted, but overall this is a strong effort in the area of planning and management. Future — Program focus will shift toward the estuary, at least in the short term, and to juvenile menhaden, as a result of life-table model predictions and the practical reality of logistical and budgetary support. With this emphasis, studies of predation on juveniles must be emphasized. An offshore effort still is needed to develop the best procedure for use of the optical particle counter to characterize temporal and spatial distributions of spawning. Plans should be developed to accomplish as much as possible, given logistical and budget constraints, to determine the temporal distribution of menhaden spawning. Coupled physical-biological models, including individual-based models, should be developed. Research planning that extends beyond the present five-year life of SABRE should be underway. Effective sampling of all early life stages, perhaps eventually including the three or four major estuarine-dependent species, should be emphasized in future research. Life-table model predictions, which now guide research planning, should be evaluated and verified. References Coastal Ocean Program. 1993. Coastal Fisheries Ecosystems (CFE). FY 1994 Implementation Plan Contract. National Oceanic and Atmospheric Administration. U.S. Department of Commerce. Washington, D.C. 40 pp. Lasker, R. (ed.). 1985. An egg production method for estimating spawning biomass of pelagic fish: application to the northern anchovy, Engraulis mordax. NOAA Technical Reports NMFS 36, 99 pp.
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A Review of the Accomplishments and Plans of the NOAA Coastal Ocean Program (1994) National Oceanic and Atmospheric Administration. 1993. National Oceanic and Atmospheric Administration 1995-2005 Strategic Plan. July 1993. U.S. Department of Commerce, Washington, D.C. South Atlantic Bight Recruitment Experiment. 1994. Report of the Second SABRE Principal Investigators' Annual Meeting, December 1993. (report prepared by L. Crowder, D. E. Hoss and P. B. Ortner). 68 pp.
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