2019 Assessment of the Alaska Plaice Stock in the Bering Sea and Aleutian Islands

Summary of Results

The survey biomass decreased 12 percent from 2018 to 2019 and is now 30 percent below the long-term average. The assessment model estimate of 3+ total biomass for 2020 is 428,800 t and the projected female spawning biomass for 2020 is 170,800 t, a value that is well-above the B40% estimate of 133,300 t. The recommended ABC for 2020 is 31,600 t based on an F40 percent = 0.125 harvest level, a 9 percent decrease from 2018. The 2020 overfishing level of 37,600 t is based on a F35 percent (0.15) harvest level. The stock is projected to be slowly declining.

Introduction

Alaska plaice (Pleuronectes quadrituberculatus) are primarily distributed on the Eastern Bering Sea continental shelf, with only small amounts found in the Aleutian Islands region. In particular, the summer distribution of Alaska plaice is generally confined to depths < 110 m, with larger fish predominately in deep waters and smaller juveniles (<20 cm) in shallow coastal waters (Zhang et al., 1998). The Alaska plaice distribution overlaps with northern rock sole (Lepidopsetta polyxystra) and yellowfin sole (Limanda aspera), but the center of the distribution is north of the center of the other two species and seems to be positioned further north in warm years and more southern in cold years. Substantial amounts of Alaska plaice were also found between St. Matthew and St. Lawrence Islands in the 2010, 2017 and 2019 northern expansions of the annual Bering Sea shelf trawl surveys.

Prior to 2002, Alaska plaice were managed as part of the “other flatfish” complex. Since then an age-structured model has been used for the stock assessment allowing Alaska plaice to be managed separately from the “other flatfish” complex as a Tier 3 single species. There has been no research on stock structure for this species.