Including predation mortality in stock assessments: a case study for Gulf of Alaska walleye pollock

Hollowed, Anne B.; Ianelli, James N.; Livingston, Patricia A.

doi:10.1006/jmsc.1999.0637

Cited by 102 publications

(97 citation statements)

References 39 publications

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“…These single-species stock assessments are used to set the biological reference points that serve as the starting point for catch advice. Multispecies stock assessments have been conducted that provide time and age-varying estimates of M for some species (e.g., Livingston and Methot 1998;Hollowed et al 2000;Jurado-Molina et al 2005). These models generally provide some ecosystem considerations that have functionally served to evaluate the level of precaution built into the catch advice arising from the single-species stock assessments.…”

Section: Discussionmentioning

confidence: 99%

In what direction should the fishing mortality target change when natural mortality increases within an assessment?

Legault

Palmer

2016

Can. J. Fish. Aquat. Sci.

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Traditionally, the natural mortality rate (M) in a stock assessment is assumed to be constant. When M increases within an assessment, the question arises how to change the fishing mortality rate target (F Target ). Per recruit considerations lead to an increase in F Target , while limiting total mortality leads to a decrease in F Target . Application of either approach can result in nonsensical results. Short-term gains in yield associated with high F Target values should be considered in light of potential losses in future yield if the high total mortality rate leads to a decrease in recruitment. Examples using yellowtail flounder (Limanda ferruginea) and Atlantic cod (Gadus morhua) are used to demonstrate that F Target can change when M increases within an assessment and to illustrate the consequences of different F Target values. When a change in M within an assessment is contemplated, first consider the amount and strength of empirical evidence to support the change. When the empirical evidence is not strong, we recommend using a constant M. If strong empirical evidence exists, we recommend estimating F Target for a range of stock-recruitment relationships and evaluating the trade-offs between risk of overfishing and forgone yield.Résumé : Traditionnellement, le taux de mortalité naturelle (M) dans une évaluation de stock est présumé être constant. Quand M augmente dans une évaluation, cela soulève la question à savoir comment changer le taux cible de mortalité par pêche (F Target ). Des considérations relatives aux recrues individuelles mènent à une augmentation de F Target , alors que le fait de limiter la mortalité totale mène à une réduction de F Target . L'application d'une ou l'autre de ces approches peut se traduire par des résultats qui n'ont aucun sens. Les augmentations à court terme du rendement associées à des valeurs de F Target élevées devraient être évaluées par rapport aux réductions potentielles du rendement futur si le taux de mortalité totale élevé se traduit par une baisse du recrutement. Des exemples basés sur la limande à queue jaune (Limanda ferruginea) et la morue franche (Gadus morhua) sont utilisés pour démontrer que F Target peut changer quand M augmente dans une évaluation et pour illustrer les conséquences de différentes valeurs de F Target . Quand la possibilité de changer M dans une évaluation est examinée, il faut d'abord prendre évaluer la quantité et la force des preuves empiriques qui appuient ce changement. Si ces preuves ne sont pas fortes, nous recommandons d'utiliser un M constant. Si les preuves empiriques sont fortes, nous recommandons d'estimer F Target pour une gamme de relations stock-recrutement et d'évaluer les compromis entre le risque de surpêche et le rendement non réalisé. [Traduit par la Rédaction]

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Section: Discussionmentioning

confidence: 99%

In what direction should the fishing mortality target change when natural mortality increases within an assessment?

Legault

Palmer

2016

Can. J. Fish. Aquat. Sci.

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“…They can be an important source of standing biomass in an ecosystem and are often subject to both predation pressure and commercial harvesting. Various authors have found that when consumption of particular forage species is calculated, the predation mortality for the species that had been assumed as a part of the total natural mortality in traditional stock assessments was underestimated (e.g., Hollowed et al 2000;Moustahfid et al 2009b). Unsurprisingly, predation mortality is temporally and ontogenetically variable as well (Tsou and Collie 2001).…”

Section: How Species Respond To Multiple Impactsmentioning

confidence: 99%

A Census of Fishes and Everything They Eat: How the Census of Marine Life Advanced Fisheries Science

O’Dor¹,

Boustany²,

Chittenden³

et al. 2012

Fisheries

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The Census of Marine Life was a 10‐year, international research effort to explore poorly known ocean habitats and conduct large‐scale experimentation with new technology. The goal of Census 2010 in its mission statement was to describe what did live in the oceans, what does live in the oceans, and what will live in the ocean. Many of the findings and techniques from census research may prove valuable in making a transition, which many governments have publicly endorsed, from single‐species fisheries management to more holistic ecosystem management. Census researchers sampled continental margins, mid‐Atlantic ridges, ocean floor vents and seeps, and abyssal plains and polar seas and organized massive amounts of past and new information in a public online database called the Ocean Biogeographic Information System (www.iobis.org). The census described and categorized seamount biology worldwide for its vulnerability to fishing, advanced large‐scale animal tracking with acoustic arrays and satellite archival tags, and accelerated species identification, including nearshore, coral reef, and zooplankton sampling using genetic barcoding and pyrotag sequencing for microbes and helped to launch the exciting new field of marine environmental history. Above all, the census showed the value of investing in large‐scale, collaborative projects and sharing results publicly.

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“…A relatively new concern for management is emerging in regions where commercial fisheries co-occur with marine mammal populations that are recovering from historical over-harvesting [2]. Increases in natural predator numbers may be influencing prey populations in ways that concern conventional fisheries stock assessment and management [2,3]. Along the west coast of Vancouver Island (WCVI), British Columbia, Canada, for example, sea otters (Enhydra lutris) were successfully reintroduced in the 1970s, and their expanding populations may now conflict with the management of high-value invertebrate fisheries that developed in their absence [4].…”

Section: Introductionmentioning

confidence: 99%

Geoduck Clam (Panopea Abrupta) Demographics and Mortality Rates in the Presence of Sea Otters (Enhydra Lutris) and Commercial Harvesting

Reidy

Cox²

2013

TOFISHSJ

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Abstract:In British Columbia, expanding sea otter (Enhydra lutris) populations are creating concerns among commercial harvesters about the potential predation impacts on exploitable geoduck clam (Panopea abrupta) stocks. We analysed fishery-independent surveys of exploited geoduck clam populations along a gradient of sea otter occupancy on the west coast of Vancouver Island, British Columbia, Canada to assess relationships between otter presence, commercial fishery removals of geoduck, and geoduck population demographics. Geoduck mean density, age composition, and estimated total mortality were influenced by a combination of variables, and therefore, we could not differentiate among geoduck populations according to sea otter presence or absence alone. As expected, we found a strong association between commercial fishery removals and geoduck clam total mortality rates. In contrast, the local numbers of sea otters were not an important factor affecting geoduck total mortality. A more balanced study design and greater sampling intensity would increase the power to detect whether sea otter predation affects harvestable geoduck stocks. Also, knowledge of the consumption rate by sea otters of geoduck throughout the year, in combination with survey data of unfished geoduck populations, would facilitate better prediction of how geoduck clam mortality rates might change as sea otters re-colonise new areas.

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Including predation mortality in stock assessments: a case study for Gulf of Alaska walleye pollock

Cited by 102 publications

References 39 publications

In what direction should the fishing mortality target change when natural mortality increases within an assessment?

In what direction should the fishing mortality target change when natural mortality increases within an assessment?

A Census of Fishes and Everything They Eat: How the Census of Marine Life Advanced Fisheries Science

Geoduck Clam (Panopea Abrupta) Demographics and Mortality Rates in the Presence of Sea Otters (Enhydra Lutris) and Commercial Harvesting

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