Uncrewed surface vehicle (USV) survey of walleye pollock, Gadus chalcogrammus, in response to the cancellation of ship-based surveys

Abstract

In 2020, the developing COVID-19 pandemic disrupted fisheries surveys to an unprecedented extent. Many surveys were cancelled, including those for walleye pollock (Gadus chalcogrammus) in the eastern Bering Sea (EBS), the largest fishery in the United States. To partially mitigate the loss of survey information, we deployed three uncrewed surface vehicles (USVs) equipped with echosounders to extend the ship-based acoustic-trawl time series of pollock abundance. Trawling was not possible from USVs, so an empirical relationship between pollock backscatter and biomass established from previous surveys was developed to convert USV backscatter observations into pollock abundance. The EBS is well suited for this approach since pollock dominate midwater fishes in the survey area. Acoustic data from the USVs were combined with historical surveys to provide a consistent fishery-independent index in 2020. This application demonstrates the unique capabilities of USVs and how they could be rapidly deployed to collect information on pollock abundance and distribution when a ship-based survey was not feasible. We note the limitations of this approach (e.g. higher uncertainty relative to previous ship-based surveys), but found the USV survey to be useful in informing the stock assessment in a situation where ship-based surveys were not possible.

Oceans of plenty? Challenges, advancements, and future directions for the provision of evidence-based fisheries management advice

“…Although fishery-independent surveys are desirable, many situations exist that make surveys infeasible due to large survey areas (e.g., entire oceanic basins for tuna species), limited manpower, dangerous conditions, or areas that are inaccessible to the survey gear (e.g., high-relief habitat). The ability to conduct acoustic surveys from uncrewed platforms could help replace or augment expensive vessel-based surveys (e.g., De Robertis et al 2021 ), thereby addressing many of these concerns using a more cost-effective approach, though lack of age- or size-composition data from acoustic surveys remains problematic. Remote video surveys can provide indices of abundance and length composition (e.g., Thompson et al 2022 ), though application may be limited to sessile species or species with strong habitat affinity (e.g., reef fish).…”

The Oceans’ Biological Carbon Pumps: Framework for a Research Observational Community Approach

“…However, these organisms may actively transport significant amounts of carbon from the EZ deep into the TZ, and thus contribute to the diel vertical migration pump (Pinti et al, 2021). Studies based on acoustic sensors carried by gliders (Reiss et al, 2021) or USV (saildrones) (De Robertis et al, 2021) have showcased the potential of this approach to monitor macrozooplankton or fish. Such technological advances may become tools of choice for characterizing diel vertical migrations of large organisms, but their role is not explicitly considered in the remainder of this paper or included in Figure 1 because the study advocating it (Pinti et al, 2021) has not been published in peer-reviewed literature as yet.…”

Quantitative processing of broadband data as implemented in a scientific split‐beam echosounder

“…The method was further developed to map the abundance of fish, driven by the need for fisheries management (Simmonds & MacLennan, 2005). More recently, fisheries acoustics sensors have been deployed on a wide range of platforms including observatories, autonomous underwater vehicles (Fernandes et al., 2003), uncrewed surface vehicles (De Robertis et al., 2021) and vessels of opportunity, observing a wide range of ecosystem processes across different spatial and temporal scales (Godø et al., 2014).…”

“…vehicles (De Robertis et al, 2021) and vessels of opportunity, observing a wide range of ecosystem processes across different spatial and temporal scales (Godø et al, 2014).…”