Size distribution of Pacific cod (Gadus macrocephalus) in the North Pacific Ocean over 6 millennia

Abstract

In this paper, we compile estimates of cod size distributions based on zooarchaeological data and contemporary length-frequency data to look at variability in size composition through time across the North Pacific, from the northern Kuril Islands through the Aleutian Islands to southeast Alaska. The results suggest that a strong longitudinal trend in cod size has remained consistent over time, with the largest cod found to the west. We find that five of nine sites show that overall cod length and distribution of the largest fish remain relatively unchanged. Two sites where we find truncation of the length distributions—or loss of the largest fish—are places where the modern fisheries have the longest history and have been most intense, suggesting a potential for anthropogenic impacts on these local populations. We acknowledge two limitations in these data: (1) there are differences in selectivity between the ancient and modern fisheries; and (2) seasonal variability in fish availability was observed to be an important explanatory variable in the modern data set, but the season of harvest is poorly understood for the ancient collections. Therefore, while differences observed between the two data sets suggest possible anthropogenic influence on the size structure of Pacific cod, they are not conclusive.

The relative influence of temperature and ontogeny on groundfish distribution varies across life stages

“…Furthermore, recent studies have reported that body size of various organisms has declined within territorial and aquatic ecosystems (Gardner et al, 2011; Sheridan & Bickford, 2011) including many fish species (Audzijonyte et al, 2020; Baudron et al, 2014; McQueen & Marshall, 2017; Oke et al, 2020) under global warming. In addition, fishing can also lead to declining fish size (Hollins et al, 2018; Link & Watson, 2019; West et al, 2020), contributing to the varying size structure observed in this study.…”

“…Annual centroids (mean ± standard deviation) of each size class of sablefish (cm) in the WGOA in warm (red), cold (blue) and medium (dark grey) years based on bottom temperature (See details about warm/cold/medium years in Li et al, 2019). The cold year of 1999 and warm year of 2015 were identified as '99' and '15' respectively. fishing can also lead to declining fish size (Hollins et al, 2018;Link & Watson, 2019;West et al, 2020), contributing to the varying size structure observed in this study.…”

Introduction to the Paleoecology of Subarctic and Arctic Seas (PESAS)

“…Formed as a working groups within the Ecosystem Studies of Subarctic and Arctic Seas (ESSAS: ) regional program, PESAS provides a context for the sharing and integration of paleo-research on atmospheric, oceanographic, marine-ecological, and human histories over time scales of millennia to centuries. PESAS embraces research spanning the last 20,000 years, from the last glacial maximum and deglacial period, when people first settled some high-latitude maritime regions (e.g., Fitzhugh 2022), to recent centuries, when massive commercial fisheries became ubiquitous and extraction came to threaten marine ecosystems globally (Pauly et al, 1998; Jackson et al, 2001, Holm et al, 2019 [this issue], West et al, 2020 [this issue]).…”

“…Pacific and Atlantic cod provide another productive pairing. Catherine West et al (2020) compare harvested Pacific cod size data from 6000 years of archaeological sites and modern commercial long-line fisheries around the North Pacific Rim (Kuril Islands to Southeast Alaska). Finding few significant differences between pre-commercial and commercial catch records, they argue that neither pre-industrial harvests nor long-term climate change had measurable effects on fish population structures (i.e., no evidence of "fishing down the food chain" with possible exception of sites in the Western Gulf of Alaska where commercial fishing had its earliest start).…”

Human Paleodemography and Paleoecology of the North Pacific Rim from the Mid to Late Holocene

“…Collaborations, initiated through the Paleoecology of Subarctic and Arctic Seas (PESAS) working group that inspired this special issue, have started assembling relevant evidence (see West et al, 2020 and Nagashima et al, 2021, in this issue). This coordinated research program promises to open new understanding of the paleoecology of the North Pacific and to extend the dynamic baselines available to contemporary ecologists, managers, and planners.…”