[MARMAM] recent publications

Paula Moreno Paula.Moreno at usm.edu
Thu Jun 14 14:01:29 PDT 2018

Dear MARMAM members,

We are pleased to announce the following two publications published in the ICES Journal of Marine Science:
Punt, A.E., Moreno, P., Brandon, J. R. and Mathews, M.A. Conserving and recovering vulnerable marine species: a comprehensive evaluation of the US approach for marine mammals
ICES Journal of Marine Science, fsy049, https://doi.org/10.1093/icesjms/fsy049
Published: 11 June 2018

Human-caused mortality due primarily to bycatch in fisheries is considered a major threat to some long-lived, slow-growing, and otherwise vulnerable marine species. Under many jurisdictions these species are designated as "protected", and fisheries are subject to a management system that includes monitoring and assessment of bycatch impacts relative to management objectives. The US management system for marine mammals is one of the most sophisticated in the world, with a limit on human-caused mortality computed using the potential biological removal (PBR), formula. Fisheries are categorized according to their impact relative to PBR, and take reduction teams established to develop take reduction plans (TRPs) when bycatch exceeds PBR. The default values of the parameters of the PBR formula were selected in the late 1990s using management strategy evaluation (MSE), but the system, in particular the classification of fisheries, has yet to be evaluated in its entirety. A MSE framework is developed that includes the PBR formula, as well as the processes for evaluating whether a stock is "strategic", assigning fisheries to categories, and implementing TRPs. The level of error associated with fisheries classification was found not to impact the ability to achieve the conservation objective established for a stock under the US Marine Mammal Protection Act (i.e. maintain or recover the stock to/at optimum sustainable population). However, this ability is highly dependent on the life history and absolute abundance of the species being managed, as well as on the premise that bycatch is reduced if bycatch is estimated to exceed the PBR. The probability of correctly classifying fisheries depends on both the coefficient of variations (CVs) of the estimates of bycatch and the marine mammal stock's abundance because classification depends on the ratio of the estimate of bycatch by fishery-type to the stock's PBR, and the precision of the former depends on the bycatch CV and the latter on the abundance estimate CV. Moreover, the probability of correctly classifying a fishery decreases for smaller populations, particularly when a fishery has low to moderate impact.

Brandon, J. R., Punt, A. E., Moreno, P., and Reeves, R. R. 2017. Toward a tier system approach for calculating limits on human-caused mortality of marine mammals. ICES Journal of Marine Science, 74: 877-887.

The Potential Biological Removal (PBR) management strategy is used for the assessment, relative to management objectives, of human-caused mortality of marine mammal stocks. PBR has been used to provide scientific advice on limits on human-caused mortality of marine mammals as well as other long-lived marine vertebrates worldwide. Current values for the parameters of this reference limit were obtained using a Management Strategy Evaluation (MSE) approach, where computer simulation is used to model a range of scenarios representing different scientific uncertainties. An assumption underlying the current management strategy, as originally evaluated, is that only the single most recent estimate of abundance is used to calculate PBR. We extend the original MSE and introduce a tiered hierarchy of data availability, from data-rich to data-poor. Alternative approaches for deriving values used to calculate PBR in each tier (e.g. incorporating multiple abundance estimates for data-rich stocks) are evaluated relative to the management objectives of the United States Marine Mammal Protection Act. A PBR tier system would allow the best available information to be used for each stock, recognizing the different types and levels of uncertainty that exist among stocks. It is shown that if the sex ratio of human caused mortality is not one, PBR may not perform as expected. Likewise, an alternative value for the NMIN percentile could be adopted when survey estimates are imprecise and multiple abundance estimates are available. The standard approach, using only a single abundance estimate, is less flexible in this regard. Additionally, incorporating multiple abundance estimates for data-rich stocks can lead to increased stability of calculated values for PBR through time. Reduction in variability could reduce regulatory uncertainty that may be associated with some human activities managed according to PBR. Therefore, including multiple abundance estimates, when possible, into the calculation of PBR may prove desirable.


Paula Moreno, Ph.D.
Fisheries, Protected Resources and Marine Spatial Ecology
University of Southern Mississippi
Gulf Coast Research Laboratory
300 Laurel Oak Drive, Ocean Springs, MS 39564
ph: (228)818.8013

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