The development of a low cost refrigerated flow-through seawater system for at-sea estimation of post-release mortality

Knotek, Ryan J.; Gill, Shaun M.; Rudders, David B.; Mandelman, John W.; Benoît, Hugues P.; Sulikowski, James A.

doi:10.1016/j.fishres.2015.05.020

Cited by 3 publications

(3 citation statements)

References 15 publications

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“…Many experimental approaches exist to estimate discard mortality, including retention trials (net‐pens, aquaria, tanks) and conventional or electronic (e.g., telemetry) tagging studies (Knotek et al 2015; Capizanno et al 2016). Each approach has advantages and disadvantages and should be selected on a case‐by‐case basis to match the characteristics of the species of interest and resources available (Benoît et al 2015).…”

Section: Methodsmentioning

confidence: 99%

“…A modular deck tank system was employed to hold holding-tank-group sea scallops for the duration of a cruise. This system was designed to examine acute (i.e., short term) postrelease mortality by modulating the seawater temperature of the system to mirror that of the bottom water observed during a cruise (Knotek et al 2015). A HOBO temperature logger (Onset Computer Corporation, Bourne, Massachusetts) was attached to the scallop dredge to record bottom temperature during a cruise.…”

Section: Field Experimentsmentioning

confidence: 99%

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Discard Mortality of Sea Scallops Placopecten magellanicus Following Capture and Handling in the U.S. Dredge Fishery

et al. 2022

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Discard mortality can represent a potentially significant source of uncertainty for both stock assessments and fishery management measures. While the family Pectinidae is considered to be robust to the capture and handling process, understanding species-specific discard mortality rates is critical to characterize both population dynamics and to develop regulatory measures to meet management objectives. The discard mortality rate for the U.S. dredge fishery of sea scallop Placopecten magellanicus was estimated empirically via a retention study aboard industry vessels under commercial conditions. Over 16,000 sea scallops were assessed via a composite index of scallop vitality that consisted of semiqualitative measures of both overt trauma (shell damage) and response to stimuli. Results indicate that overall sea scallop discard mortality was 21% and consistent with the values currently assumed in the stock assessment. Survival mixture models support the utility of a simple metric of physical trauma as an effective predictor of mortality. Exposure time was also identified as a positively correlated factor that was important in describing the discard mortality process. Application of experimental results highlight the need to consider some operational characteristics of the fishery to reduce potential discard mortality.

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Section: Methodsmentioning

confidence: 99%

Section: Field Experimentsmentioning

confidence: 99%

Discard Mortality of Sea Scallops Placopecten magellanicus Following Capture and Handling in the U.S. Dredge Fishery

et al. 2022

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“…Discard mortality rates, which represent the combined at‐vessel mortality (AVM) and postrelease mortality (PRM), are typically estimated with experiments that simulate fishery conditions and subsequently observe the fate of discarded individuals (Pollock and Pine 2007). These observations can be generated via a variety of methods, including containment of experimental subjects (i.e., field net pens or on‐deck holding tanks; Mandelman et al 2013; Knotek et al 2015), traditional mark–recapture studies (Rudershausen et al 2014), or electronic monitoring and/or biotelemetry approaches (Capizzano et al 2016, 2019; Knotek et al 2020). The use of electronic tags has grown more common because unlike confinement studies, this approach better reflects the discarding process wherein tagged animals are able to swim freely and interact with their environment after being discarded (Portz et al 2006; Pollock and Pine 2007).…”

mentioning

confidence: 99%

Determining Discard Mortality of Monkfish in a Sea Scallop Dredge Fishery

Weissman

Knotek

Mandelman

et al. 2021

N American J Fish Manag

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Discard mortality studies are considered a primary research priority, particularly for species and fisheries where discard rates are high. Monkfish (the commercial name for Goosefish) Lophius americanus supports the most lucrative finfish fishery in New England, and it is also the second highest bycatch species by weight in the sea scallop dredge fishery. Despite its commercial importance, no data exist with respect to monkfish discard mortality estimates for any gear type. The goals of this study were to evaluate the discard mortality process for monkfish captured in sea scallop dredge gear, estimate mortality rate, and develop best handling/management practices to mitigate the impact of monkfish bycatch in the sea scallop dredge fishery. Discard mortality was estimated during a field study conducted between June and October 2017 on board sea scallop commercial fishing vessels on Georges Bank in the Northwest Atlantic. Pop‐up satellite tags were affixed to 60 monkfish to track survival from 14 to 28 d postcapture. From these monitored individuals, high predation rates were observed (n = 18 out of 26 mortalities), and the bulk of mortalities (n = 21) occurred within the first 24 h of discarding. However, in light of having no clear method for disentangling capture‐related and tag‐induced predation, predation was noted exclusively as one or the other to account for uncertainty and provide an upper and lower bound of mortality. This approach suggested that the discard mortality rate was between 17.9% and 54.1% for monkfish discarded by scallop dredges and that elevated air temperatures (above thermal preferences) may contribute to increased mortality. Based on these results, it appears that monkfish discard mortality is lower than previous assumptions of 100%, and potential best‐practice management suggestions moving forward may include minimizing fishing in areas of high monkfish abundance or scheduling rotating time/area closures during periods when air temperature exceeds monkfish thermal tolerance of 13°C.

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