Depth zonation and latitudinal distribution of deep-sea scavenging demersal fishes of the Mid-Atlantic Ridge, 42 to 53°N

Abstract

Scavenging fishes of the Mid-Atlantic Ridge (MAR) were investigated using a baited autonomous lander equipped with a time-lapse camera between 924 and 3420 m water depth along 3 east -west transects at 42, 51 and 53°N across the MAR. We photographed 22 taxa at bait. Community structure analysis revealed 3 main assemblages, shallow (924 to 1198 m), intermediate (1569 to 2355 m) and deep (2869 to 3420 m), dominated by 3 species, Synaphobranchus kaupii, Antimora rostrata and Coryphaenoides (Nematonurus) armatus, respectively. Abyssal species in the axial valley region were C. armatus, Histiobranchus bathybius and Spectrunculus sp. Compared with continental margin regions A. rostrata were abundant and grew to a large size in the 2 northern transects, whereas S. kaupii were reduced in abundance and maximum depth of occurrence. The size, abundance and depth distribution of C. armatus was consistent with the hypothesis that these fish are part of a population mixing freely across the deep North Atlantic Basin. Temperature and latitude influenced distribution. (1) Five taxa were found only in the southern transect: Pseudotriakis microdon, Centroscymnus coelolepis, Simenchelys parasitica, Anguilliformes sp. and Lepidion 1 sp.

A novel method to obtain accurate length estimates of carnivorous reef fishes from a single video camera

“…In their design there was a short space between the bottom and the reference scale, so fishes could swim or rest a few centimeters behind it (Priede et al, 1994). As only those fishes at the level of, or behind, the reference scale were measured, errors were more likely underestimates of fish length (King et al, 2006(King et al, , 2008. In other cases the frame, which rested on the seabed, was directly marked to provide a reference scale, so fish size was most probably overestimated .…”

“…The first of these was the calibration function used to estimate CF. Another function, used to compare the performance of the MBUV with other methods (e.g., Priede et al, 1994;King et al, 2006;Gardner & Struthers, 2012), allowed estimating the distance of a given object to the reference scale included in the image (hereafter referred as 'Height' model). For the calibration model, CF was regressed on the NL/LRI ratio.…”

“…We used the same selected video sections and applied the RSB method (Priede et al, 1994;King et al, 2006King et al, , 2008 for comparison purposes.…”

Response of deep-sea scavengers to ocean acidification and the odor from a dead grenadier

“…Amphipods may be responsible for much of the consumption of some food falls, and fall prey to macrourids, liparids, zoarcids, or other predators. Typically, only large macrourids are photographed at bait (King et al 2006), and only large specimens have carrion in their stomachs (Drazen et al 2001), suggesting that small individuals are unable to compete for resources at food falls or actively avoid them due to predation risk. Ontogenetic increases in the size of the olfactory lobe of Coryphaenoides armatus indicate a shift from visual to olfactory cues (Wagner 2003), which may also influence the reduced response of small macrourids to odor plumes.…”

“…Scavenger assemblages vary by region, with decreasing species richness with depth (Priede & Bagley 2000, King et al 2006, and respond variably to the type, size, and position of bait (Wolff 1976, Rowe et al 1986, Witte 1999, Kemp et al 2006. At bathyal depths, megafaunal invertebrates are important scavengers (e.g.…”