Diets of deepwater oreos (Oreosomatidae) and orange roughy Hoplostethus atlanticus

Abstract

The diets of black oreo Allocyttus niger, smooth oreo Pseudocyttus maculatus, spiky oreo Neocyttus rhomboidalis and orange roughy Hoplostethus atlanticus were determined from examination of contents of 240, 311, 76 and 415 non-empty stomachs, from fishes sampled by bottom trawl on Chatham Rise to the east of South Island, New Zealand. Hoplostethus atlanticus had an opportunistic predatory strategy with a broad diet dominated by prawns and mesopelagic teleosts, but with substantial components of mysids and cephalopods. Pseudocyttus maculatus was strongly specialized on gelatinous zooplankton (jellyfish and salps). Allocyttus niger consumed mainly salps and hyperiid amphipods, and to a lesser extent fishes, prawns, mysids and copepods. Neocyttus rhomboidalis primarily consumed salps, along with mysids, euphausiids and fishes. Only P. maculatus did not exhibit significant ontogenetic variation in diet. The diets were also influenced by year and bottom depth. Differences in the distributions and diets of the four species probably reduce conflicts in resource use.

Prey size spectra and predator to prey size ratios of southern ocean salps

“…The cruise consisted of 5 quasi-Lagrangian experiments (hereafter “cycles”) lasting 4-8 days each, with only 4 cycles (Cycle 1-4) showing significant salp presence (Figure 2). Cycle locations were chosen based on net tows through regions with high potential for salp presence according to previous observations on habitat distributions of salp-eating demersal fish (Forman et al 2016; Horn et al 2011).…”

“…Furthermore, as salps themselves are part of the diet of at least 202 marine species, salps may not act as a net carbon sink as classically believed but instead increase trophic transfer and vertical export efficiencies (Michaels and Silver, 1988; Henschke et al 2016). Their presence could thus support economically important species like mackerel (Nishimura 1958), bluefin tuna (Cardona et al 2012), anchovies (Mianzan et al 2001), and other demersal fishes (Horn et al 2011; Forman et al 2016). However, the physiological ability to feed at PPSRs up to 10,000:1 does not necessarily mean that this is the range over which most salps feed.…”

Salp blooms increase carbon export 5-fold in the Southern Ocean

“…The problem of finding salp blooms to conduct this study was addressed by capitalizing on knowledge of ‘salp-eating’ New Zealand deep-sea fishes: oreos (Oreosomatidae) and warehous ( Seriorella spp.) 18,19 . Their well-defined demersal habitat areas over the Chatham Rise 18,19 were successfully used to target our salp-bloom search.…”

“…18,19 . Their well-defined demersal habitat areas over the Chatham Rise 18,19 were successfully used to target our salp-bloom search. Five water parcels (hereafter referred to as ‘cycles’) were investigated.…”