Routine metabolic rates of pelagic marine fishes and cephalopods as a function of body mass, habitat temperature and habitat depth

Abstract

Routine metabolic rates of pelagic marine fishes and cephalopods as a function of body mass, habitat temperature and habitat depth Tsutomu Ikeda 16-3-1001 Toyokawa-cho, Hakodate 040-0065, Japan a b s t r a c t Cephalopods and fishes are major components of marine micronekton and nekton, so an understanding of their physiology and roles in ocean biogeochemistry is important. I compiled the routine respiration rates (50 datasets on 41 cephalopod species; 102 datasets on 90 fish species) from various depth horizons (b1300 m) of the world's oceans and analyzed these rates as a function of body mass [wet mass (WM), dry mass (DM), carbon (C) or nitrogen (N)], habitat temperature and habitat depth using multiple regression. Stepwise-regression analyses revealed that body mass was the most important parameter, followed by habitat temperature and habitat depth, and these variables explained 89.7-93.8% and 94.7-95.8%, respectively, of the variance in the respiration data of fishes and cephalopods. The addition of a taxon category (order or family) as a fourth variable improved these correlations only slightly (95.6-95.7% and 95.7-96.2%, respectively). The resultant regression equation showed higher respiration rates in cephalopods than fishes relative to the DM, C or N body mass (by a factor 1.5-to 1.7-fold), but not to the WM body mass. The O:N ratios (respiration/ammonia excretion, by atoms) reported for 6 cephalopods (median: 13.2) and 35 fishes (24.2) suggested the predominance of protein as a metabolite in the former and carbohydrate or lipid in the latter. The present results are discussed in light of the methodological constraints and standing hypothesis for the relationship between the metabolic rate and temperature. The empirical models established in the present study can be used to assess the roles of cephalopods and fishes in C and N cycles in pelagic ecosystems based on the organisms' body mass spectra, ambient temperatures and depth distributions.

Polymorphism and multiple correlated characters: Do flatfish asymmetry morphs also differ in swimming performance and metabolic rate?

“…The average RMR of P. stellatus in our study was 134.04 mg O 2 hr −1 kg −1 ; comparable to those found across fish taxa (Bond, 2007;Ikeda, 2016), but relatively high compared to reports from other flatfishes (Duthie, 1982;Priede & Holliday, 1980). One explanation is that our flounder were juveniles, all 16.0 cm SL or less, while flatfish used in these other studies were adults of ~30.0 cm SL.…”

Do squids breathe through their skin?

“…The O:N ratios observed here were higher than is typical for squid (11-17), which have a well-known protein-rich diet (Ikeda, 2016). One animal was fasted for 3 days and had a notably higher O:N ratio than any other individual, suggesting a use of lipid reserves.…”

Mesozooplankton and Micronekton Active Carbon Transport in Contrasting Eddies

“…Contrary to Hidaka et al (2001), we found that mesozooplankton contributed more to downward carbon export than micronekton in the B-CCE and WCE, while only micronekton were contributing to export in the R-WCE. This difference was primarily driven by the higher metabolic rates, and thus respiratory flux, of mesozooplankton when compared to micronekton (Ikeda, 1985(Ikeda, , 2016. However, our sampling was concentrated in eddy centers, so it is possible that we missed the portion of micronekton that is thought to aggregate at eddy peripheries (Sabarros et al, 2009;Drazen et al, 2011).…”

“…The uncertainty associated with the models may indeed plague such estimates. Respiration was estimated using empirical allometric relationships dependent on carbon weight and in situ temperature from the literature (Ikeda, 2013b(Ikeda, , 2014(Ikeda, , 2016Henschke et al, 2019). For all relationships used, temperature and weight explained >86% of the variation in oxygen uptake, suggesting minimal uncertainty with the models.…”

“…Once at depth, these organisms metabolize surface-derived nutrients releasing carbon by way of respiration, dissolved organic carbon (DOC) excretion, gut flux, and mortality (Steinberg et al, 2000;Ducklow et al, 2001;Davison et al, 2013;Steinberg and Landry, 2017). As these processes are largely size, temperature, and pressure dependent they can therefore be calculated for whole communities by applying a size-based approach (Zhang and Dam, 1997;Steinberg et al, 2000;Ikeda, 2013aIkeda, , 2014Ikeda, , 2016. Larger organisms likely transport more carbon due to their deeper migrations (Sameoto et al, 1987;Moteki et al, 2009), body size/mass (Hansen and Visser, 2016), large fecal pellets (Turner, 2002), and long gut passage times (GPTs) (Baird et al, 1975;Dagg and Wyman, 1983;Reinfelder and Fisher, 1994;Pakhomov et al, 1996).…”