Length–weight relationships of mesopelagic fishes from the equatorial and tropical Atlantic waters: influence of environment and body shape

Abstract

Length-weight relationships (LWRs) were estimated for 36 mesopelagic fish species collected from the equatorial and tropical Atlantic encompassing several oceanographic regions: oligotrophic, equatorial, Cape Blanc, Cape Verde and the Canary Islands. The sample was composed of myctophids (25 species), gonostomatids (5), sternoptychids (3), stomiids (2) and phosichthyids (1). The species were clustered according to body shape: "short-deep" (sternoptychids), "elongate" (gonostomatids, stomiids and some phosichthyids) and "fusiform" (myctophids and some phosichthyids). Three types of weight and LWRs were considered: wet weight (WW), eviscerated wet weight (eWW) and eviscerated dry weight (eDW). The study demonstrated that most species present a positive allometric growth, independent of the weight used. However, the allometric value varied in 40-50% of species depending on the type of weight considered. Significant variations linked to fish morphology were found in the relationship between the slope and intercept of the LWR equation. Significant differences were also noted in the water content linked to fish body shape. Based on the distributions of several species we compare their fitness between oceanographic regions using the relative condition factor (K rel). Except for Diaphus brachycephalus (oligotrophic vs. equatorial waters) and Lampanyctus alatus (equatorial, Cape Blanc, Cape Verde and the Canary Islands), no regional significant differences were observed in the species analysed.

Length–weight relationships of 55 mesopelagic fishes from the eastern tropical North Atlantic: Across‐ and within‐species variation (body shape, growth stanza, condition factor)

“…Our study confirms the earlier observed influence of body shape on the parameters of LWRs in fishes in general and mesopelagic fishes in particular (Froese, 2006;L opez-Pérez et al, 2020) 3). Geographic regions are indicated by linetype, symbol and colour (EQ-C, dotted line, dark-blue square; EQ-N, two-dashed line, turquoise triangle; LO-E, solid line, red circle; LO-W, dashed line, violet diamond).…”

“…representative size ranges reported up to now (Battaglia et al, 2010;Eduardo et al, 2019Eduardo et al, , 2020aJiang et al, 2017;L opez-Pérez et al, 2020;Olivar et al, 2013;Sarmiento-Lezcano et al, 2018;Slayden, 2020;Wang et al, 2018). In 31 species, body lengths were within the maximum range of body lengths recorded in the area, with new records of maximum lengths for 13 species.…”

“…Depending on the season, the geographic population and annual differences in environmental conditions, LWRs in individual species can vary substantially (Froese, 2006), but sampling gear and methodology also impact the size ranges sampled and, consequently, their size‐based parameters (Gartner et al ., 1989; Harrisson, 1967; Heino et al ., 2011; Jamieson et al ., 2006; Kaartvedt et al ., 2012; Kashkin & Parin, 1983; Pearcy, 1983). LWRs in mesopelagic fish species have been reported in comparatively few studies (Battaglia et al ., 2010; Eduardo et al ., 2019, 2020a; Grimaldo et al ., 2020; Jiang et al ., 2017; López‐Pérez et al ., 2020; Olivar et al ., 2013; Sarmiento‐Lezcano et al ., 2018; Slayden, 2020; Wang et al ., 2018). Studies are not always comparable due to differences in preservation strategies employed that further affect LWR estimates.…”

Short‐term exposure of 17α‐ethynylestradiol impairs water homeostasis by inhibiting osmoregulatory and cortisol regulating genes in adult zebrafish

“…For measurements of water weight and water content, 3 fish in each tank were sacrificed and dried for 1 h at 105°C and then weighted. Water weight (=weight before drying−weight after drying) and water content (=water weight/body weight × 100%) ( N = 9 for each group) were calculated thereafter (López‐Pérez et al, 2020). Eight fish were tail‐docked for blood sampling as described by Babaei et al (2013).…”

The global ocean size-spectrum from bacteria to whales

“…To define the size range of mesopelagic fish, we used the minimum and maximum recorded sizes from three datasets of mesopelagic fish length-weight measurements (85)(86)(87). The combined datasets contained samples from the trophic and equatorial Atlantic as well as the Southern Ocean and gave a body size range of 0.01-500gm for mesopelagic fish.…”