Diet and life history reduce interspecific and intraspecific competition among three sympatric Arctic cephalopods

Abstract

Trophic niche and diet comparisons among closely sympatric marine species are important to understand complex food webs, particularly in regions most affected by climate change. Using stable isotope analyses, all ontogenetic stages of three sympatric species of Arctic cephalopods (genus Rossia) were studied to assess inter- and intraspecific competition with niche and diet overlap and partitioning in West Greenland and the Barents Sea. Seven traits related to resource and habitat utilization were identified in Rossia: no trait was shared by all three species. High boreal R. megaptera and Arctic endemic R. moelleri shared three traits with each other, while both R. megaptera and R. moelleri shared only two unique traits each with widespread boreal-Arctic R. palpebrosa. Thus all traits formed fully uncrossing pattern with each species having unique strategy of resource and habitat utilization. Predicted climate changes in the Arctic would have an impact on competition among Rossia with one potential ‘winner’ (R. megaptera in the Barents Sea) but no potential ‘losers’.

The significance of cephalopod beaks as a research tool: An update

“…Currently neither bulk nor compound-specific SIA allows the identification of specific prey species. Even if the measurement of δ 13 C and δ 15 N values in a specific target prey species is performed, it is difficult to confirm that the tested species was eaten rather than another species with similar diet and trophic level (Fogel and Tuross, 2003;Naito et al, 2013;Pinkerton et al, 2014;Golikov et al, 2020). So-called mixed models are commonly used to infer predator diet composition from bulk SIA data.…”

“…Cephalopod beaks can also provide considerable information on a wide range of physiological, biological and ecological traits, including cephalopod availability, consumption of cephalopods, migrations, competition between cephalopod predators, levels of cephalopod scavenging by predators, distribution, age, growth, cohorts, life-events, stress, thermal changes, reproduction, feeding ecology, behavior, spawning areas, post-spawning mortality and sexual dimorphism [e.g., see review in Xavier et al (2016) and Arkhipkin et al (2018); Table 1]. More recently, new emergent techniques for work on beaks (e.g., stable isotope and trace elements analyses, geometric morphometrics and microstructure analysis) have provided further information on habitat and trophic position, composition, contamination, response of cephalopods to climate variability at individual and/or population levels, embryonic morphogenesis, paralarval ontogeny, ecology and age estimation (Cherel and Hobson, 2005;Perales-Raya et al, 2014b;Xavier et al, 2016;Perales-Raya et al, 2018;Queirós et al, 2018;Golikov et al, 2019a;Golikov et al, 2019b;Northern et al, 2019;Abreu et al, 2020;Queirós et al, 2020a;Armelloni et al, 2020;Queirós et al, 2020b;Franco-Santos and Vidal, 2020;Golikov et al, 2020;Perales-Raya et al, 2020;Fang et al, 2021b;Lishchenko and Jones, 2021). Consequently, the importance of cephalopod beaks in ecological studies continues to attract attention and recognition, with various workshops being organised (Clarke, 1986;Xavier et al, 2007a;Jackson et al, 2007;Xavier et al, 2015).…”

Life History of the Arctic Squid Gonatus fabricii (Cephalopoda: Oegopsida) Reconstructed by Analysis of Individual Ontogenetic Stable Isotopic Trajectories

“…Values of δ 15 N in cephalopod beaks, in contrast to δ 13 C values, are on average 4.8‰ lower than values from muscle tissue [ 72 , 75 , 87 , 88 ]. Therefore, when estimating TL, we added 4.8‰ to raw beak δ 15 N values as proposed by Cherel et al [ 88 ] and Golikov et al [ 27 , 28 , 30 , 76 ].…”

“…Cephalopoda (Phylum Mollusca) are an abundant group of marine invertebrates in Arctic marine ecosystems, are known to respond rapidly to environmental change, and have a pivotal role in the food web [ 23 , 25 , 26 , 27 , 28 , 29 ]. Eleven species of cephalopods complete their life cycle in the Arctic [ 23 , 30 ], and they are ecologically important due to their high abundances and biomasses [ 29 , 31 , 32 ]. For example, cirrate octopod density can reach up to 94 ind.…”

“…Carbon ( δ 13 C) and nitrogen ( δ 15 N) are the most frequently used stable isotopes to investigate trophic relationships in marine food webs [ 73 , 74 ]. Stable isotope analysis has been used on cephalopods to reveal their foraging habitat changes, migrations, and dietary changes throughout their ontogeny e.g., [ 30 , 47 , 50 , 51 , 52 , 75 , 76 ]. Specific SIA studies on G. fabricii with different ML demonstrated an increase of δ 15 N values from small to large individuals, suggesting a change in the food spectra from low to high trophic level (TL) prey as squid grow [ 27 , 77 ].…”