Multiple life‐stage connectivity of Pacific halibut (Hippoglossus stenolepis) across the Bering Sea and Gulf of Alaska

Abstract

Pacific halibut (Hippoglossus stenolepis) is managed as a single stock throughout the Gulf of Alaska (GOA) and eastern Bering Sea (BS), but biogeographical barriers and the potential for differential impacts of climate change may alter habitat use and distributions, and restrict connectivity between these ecosystems. To improve our understanding of larval dispersal pathways and migrations of young fish within and between GOA and BS, we (a) examined potential pelagic larval dispersal and connectivity between the two basins using an individual‐based biophysical model (IBM) focusing on years with contrasting climatic conditions and (b) tracked movement of fish up to age‐6 years using annual age‐based distributions and a spatiotemporal modeling approach. IBM results suggest that the Aleutian Islands constrain connectivity between GOA and BS, but that large island passes serve as pathways between these ecosystems. The degree of connectivity between GOA and BS is influenced by spawning location such that an estimated 47%–58% of simulated larvae from the westernmost GOA spawning location arrived in the BS, with progressive reductions in connectivity from spawning grounds further east. From the results of spatial modeling of 2‐ to 6‐year‐old fish, we can infer ontogenetic migration from the inshore settlement areas of eastern BS toward Unimak Pass and GOA. The pattern of larval dispersal from GOA to BS, and subsequent post‐settlement migrations back from BS toward GOA, provides evidence of circular, multiple life stage, connectivity between these ecosystems, regardless of climatic variability or year‐class strength.

Integrating seabird dietary and groundfish stock assessment data: Can puffins predict pollock spawning stock biomass in the North Pacific?

“…Given no leading relationships between EBS SSB and Aiktak age‐0 pollock, however, this connectivity appears uni‐directional from WGoA to EBS, and no corresponding relationship from the EBS stock to the WGoA stock. This directional larval drift has also been identified for other groundfish (Sadorus et al, 2021). In summary, Aiktak Island appears to be the prime location for sampling age‐0 walleye pollock since sampling there indicates the proportion of the age‐0 population advected to the edge of the WGoA range and also the WGoA production that may determine EBS SSB 1–3 years later.…”

“…This idea matches modelled results of Hinckley et al (2016) suggesting that as larvae are swept downstream from Shelikof Strait to the eastern Aleutian Islands they grow to sufficient size and are targeted by puffins as prey when they reach ~30-50 mm (Figure 2). Indeed, Hatch and Sanger (1992) has also been identified for other groundfish (Sadorus et al, 2021).…”

Impact of warming and deoxygenation on the habitat distribution of Pacific halibut in the Northeast Pacific

“…Unknown future changes in habitat availability could exacerbate this trend, or open new habitat regions for Pacific halibut. Given the large degree of interconnectivity of Pacific halibut in the Northeast Pacific (Sadorus et al, 2021), future studies on climate change impacts would benefit from considering the full range of Pacific halibut distribution, for example by utilizing a high‐resolution global earth system model. Continued sampling of oceanographic and fisheries‐independent Pacific halibut abundance data will extend the observation‐based time series of environmental variables, and contribute to a better understanding of the relationship between Pacific halibut interannual variability and oceanographic properties.…”

“…4). This species is distributed over the majority of the North American Pacific coast, from central California to the Bering Sea (Sadorus et al, 2021), and is regulated and surveyed by the International Pacific Halibut Commission (IPHC). Since 1997, the number of Pacific halibut counted in fisheries‐independent surveys has declined persistently along the entire IPHC regulatory areas, from Alaska to California (Stewart & Wilson, 2020).…”

Genetic connectivity in Twospot flounder (Bothus robinsi) across the Gulf of Mexico, inferred with single nucleotide polymorphisms from larvae and adults

“…For B. robinsi, there is a record suggesting the possibility for PLD as long as 5-12 months (Evseenko, 2008). Flatfishes from the Order Pleuronectiformes are characterized by long PLD, for example, 70 days for the Bay whiff (Citharichthys spilopterus; Gunther, 1862) (Joyeux et al, 1995), and 4-7 months for the Atlantic halibut (Hippoglossus hippoglossus; Linnaeus, 1758) (Sadorus et al, 2021).…”