Predicting habitat use by the Argentine hake Merluccius hubbsi in a warmer world: inferences from the Middle Holocene

Abstract

Fish skeletal remains recovered from two archaeological sites dated in the Middle Holocene of Tierra del Fuego (Argentina) were analysed to describe habitat use patterns by hake in the past and predict changes in a warmer world. Mitochondrial DNA was successfully extracted and amplified from 42 out of 45 first vertebra from ancient hake and phylogenetic analysis assigned all haplotypes to Argentine hake (Merluccius hubbsi). According to osteometry, the Argentine hake recovered from the archaeological site were likely adults ranging 37.2-58.1 cm in standard length. C and N stable isotope analysis showed that currently Argentine hake use foraging grounds deeper than those of Patagonian blenny and pink cusk-eel. Argentine hake, however, had a much broader isotopic niche during the Middle Holocene, when a large part of the population foraged much shallower than contemporary pink cusk-eel. The overall evidence suggests the presence of large numbers of Argentine hake onshore Tierra del Fuego during the Middle Holocene, which allowed exploitation by hunter-gatherer-fisher groups devoid of fishing technology. Interestingly, average SST off Tierra del Fuego during the Middle Holocene was higher than currently (11 °C vs 7 °C) and matched SST in the current southernmost onshore spawning aggregations, at latitude 47 °S. This indicates that increasing SST resulting from global warming will likely result into an increased abundance of adult Argentine hake onshore Tierra del Fuego, as during the Middle Holocene. Furthermore, stable isotope ratios from mollusc shells confirmed a much higher marine primary productivity during the Middle Holocene off Tierra del Fuego. Keywords Hake • Osteometry • Stable isotopes • Tierra del Fuego • ZooarchaeologyCommunicated by Leon A. Barmuta.

A millennium of trophic stability in Atlantic cod (Gadus morhua): transition to a lower and converging trophic niche in modern times

“…Moreover, some of the observed variation in δ 13 C could reflect local variation in primary production or prey species rather than larger patterns of temperature and ocean baseline values. Notably, the upturn of the δ 13 C values of wolffish in present times could suggest that wolffish, in contrast to the gadoid species, are now more dependent on inshore production and this is in fact supported by present day stomach content analysis 62 . If this development continuous it could signal the recurrent divergence of the niches of those demersal fish, following centuries of fishery driven convergence.…”

“…Conversely, it is possible that the historical niche of wolffish shifted due to competitive release, bringing the trophic niche of wolffish closer to other demersal fish species. Previous studies have found niche width and niche overlap within communities to change significantly between pristine and modern ecosystems 38 , 39 , 62 and trophic shifts in fish are known to follow competitive release by the reduction of larger or dominant fish species 37 , 63 . The present-day trophic niche of wolffish is very different from Atlantic cod and it may be more subject to local change in prey availability and disruption to nearshore benthic production as wolffish forage mainly on echinoderms and other benthic invertebrates and less on fish 64 , and this may be reflected in the fluctuating niche observed for wolffish (Figs.…”

Trophic structure of southern marine ecosystems: a comparative isotopic analysis from the Beagle Channel to the oceanic Burdwood Bank area under a wasp-waist assumption

“…As juveniles, these species can at least temporally dominate the WW level, but as adults, they became semi-demersal or demersal predators (Bakun 2006). These mesopredators may constitute an important alternate food supply available to top predators in CA (Bas et al 2020, Nye et al 2020, where we found a more complex system than in the BC and BB areas (e.g. higher values of community-wide metrics).…”

“…Benthic primary consumers were considered as baseline 2 (b2). We used the δ 15 N and previously published δ 13 C values (mean ± SD) of Nacella magellanica for CA (δ 15 N = 11.9 ± 0.3 ‰ and δ 13 C = −8.5 ± 2.0 ‰, Bas et al 2020); N. deaurata for BC (δ 15 N = 12.1 ± 0.6 ‰ and δ 13 C = −15.1 ± 1.4 ‰, Riccialdelli et al 2017a) and ascidians for BB (δ 15 N = 4.2 ± 0.8 ‰ and δ 13 C = −21.7 ± 1.1 ‰, L. Riccialdelli unpubl. data).…”

“…Warmer (e.g. Argentine hake M. hubbsi, Bas et al 2020) and oceanic shoaling pelagic species (e.g. snoek Thyrsites atun, Zangrando et al 2016) may have played an important role as WW species in the past.…”