Although many countries have formally committed to Ecosystem-Based Fisheries Management (EBFM), actual progress toward these goals has been slow. This paper presents two independent case studies that have combined strategic advice from ecosystem modeling with the tactical advice of single-species assessment models to provide practical ecosystem-based management advice. With this approach, stock status, reference points, and initial target F are computed from a single-species model, then an ecosystem model rescales the target F according to ecosystem indicators without crossing pre-calculated single-species precautionary limits. Finally, the single-species model computes the quota advice from the rescaled target F, termed here Feco. Such a methodology incorporates both the detailed population reconstructions of the single-species model and the broader ecosystem perspective from ecosystem-based modeling, and fits into existing management schemes. The advocated method has arisen from independent work on EBFM in two international fisheries management systems: (1) Atlantic menhaden in the United States and (2) the multi species fisheries of the Irish Sea, in the Celtic Seas ecoregion. In the Atlantic menhaden example, the objective was to develop ecological reference points (ERPs) that account for the effect of menhaden harvest on predator populations and the tradeoffs associated with forage fish management. In the Irish Sea, the objective was to account for ecosystem variability when setting quotas for the individual target species. These two exercises were aimed at different management needs, but both arrived at a process of adjusting the target F used within the current single-species management. Although the approach has limitations, it represents a practical step toward EBFM, which can be adapted to a range of ecosystem objectives and applied within current management systems.

Isotopically labeled nitrate ( 15 NO ) was added continuously to the Rowley estuary, Massachusetts, for 22 d to Ϫ 3 assess the transport, uptake, and cycling of terrestrially derived nitrogen during a period of high river discharge and low phytoplankton activity. Isotopic enrichment of the 3.5-km tidal prism (150,000 m 3 ) was achieved for the 3 weeks and allowed us to construct a nitrogen mass balance model for the upper estuary. Mean ␦ benthos and was evenly split between direct denitrification and autotrophic assimilation. The lack of water-column 15 N uptake was attributed to low phytoplankton stocks and short water residence times (1.2-1.4 d). Uptake of watercolumn NO by benthic autotrophs (enriched in excess of 100‰) was a function of NO concentration and satisfiedup to 15% and 25% of the total nitrogen demand for benthic microalgae and macroalgae, respectively. Approximately 10% of tracer assimilated by benthic autotrophs was mineralized and released back to the water column as 15 NH . By the end of the study, 15 N storage in sediments and marsh macrophytes accounted for 50%-70% of the ϩ 4 15 N assimilated in the estuary. These compartments may sequester watershed-derived nitrogen in the estuary for time scales of months to years.

A grazlng zooplankter may minimize its suscept~bil~ty to v~s u a l predat~on by r e d u c~n g its gut contents or ~t s f e e d~n g movements Such behav~oral rnechan~sms require (1) that the prey can detect the predator and (2) that ~t reduces its grazing activity when l~g h t c o n d~t~o n s favor visual predation In this work we have e x a m~n e d the grazing act~vity of 2 estuarine copepods Acart~a tonsa and Acartla hudsonlca in the chemical presence or absence of ~t s natural visual predator the Atlantic sllverside Meludia menidia Our results ind~cate that in the presence of chemical exudates of M rnenldla A tonsa and A hudsonica reduced their gut fullness T h~s response was observed only when l~g h t levels wele high enough for visual predation Reduct~on in gut fullness resulted from decreased ingestion rates, not from changes in gut evacuation rates Light intensity was found to affect the grazlng response to the fish-exuded chemical(s) Such behavior may be advantageous to these copepods in estuaries which contain large numbers of v~s u a l predators KEY WORDS: Acartia tonsa. Acartia hudsonica. Menjdia menidla. Visual predation. Nocturnal feeding. Copepod grazlng. Copepod behavior. Fish exudates O Inter-Research 1999 Resale of full artlcle not permitted

Garrison, L. P., Link, J. S., Kilduff, D. P., Cieri, M. D., Muffley, B., Vaughan, D. S., Sharov, A., Mahmoudi, B., and Latour, R. J. 2010. An expansion of the MSVPA approach for quantifying predator–prey interactions in exploited fish communities. – ICES Journal of Marine Science, 67: 856–870. Ecosystem-based fisheries management requires tools to place fish-stock dynamics in the broader context of fishery, predator, and competitive removals. Multispecies virtual population analysis (MSVPA) is an approach to quantifying predator–prey interactions and estimating the rates of predation mortality for exploited fish populations. Here, an extended MSVPA (MSVPA-X) is presented as an alternative to existing MSVPA approaches. Notably, MSVPA-X uses index-tuned VPA methods, applies a more flexible feeding model, and includes an alternative functional feeding response. The MSVPA-X model is applied to a western Atlantic fish community, focusing on Atlantic menhaden and its major fish predators, and a sensitivity analysis of major model parameters is presented. The sensitivity analysis highlights the need for adequate diet sampling. The MSVPA-X represents an improvement over previous approaches by increasing the flexibility to model seasonal and interannual dynamics in the strength of predator–prey interactions. Model results demonstrate that, for menhaden in particular, and forage fish in general, quantifying predation mortality is an important part of effective assessments of forage fish, their predators, and the fisheries of both.

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