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

Abstract

Experiments to assess the impact of ocean acidification on abyssal animals were performed off Central California. The survival of caged megafauna (Benthoctopus sp., Pachycara bulbiceps, Coryphaenoides armatus) exposed to CO 2 -rich and normal (control) seawater varied among species. Benthoctopus sp. and P. bulbiceps survived control conditions and month-long episodic exposure to acidic, CO 2 -rich waters (pH reductions of ~0.1 U). All C. armatus in both treatments died, potentially due to cage-related stress, predation, and exposure to acidic waters. High survival by P. bulbiceps and Benthoctopus under month-long exposure to CO 2 -rich waters indicates a physiological capacity to cope, at least temporarily, with stresses that will accompany expected future changes in ocean chemistry. The abundance of free-ranging scavengers was not correlated with variation in pH levels near fish cages. Incidental observations of abyssal scavengers collected using time-lapse cameras during these experiments were used secondarily to evaluate the hypothesis that macrourid fishes avoid the odor of dead conspecifics. Caged macrourids in view of time-lapse cameras died within 2 to 3 d, eliciting a strong response from the regional scavenger assemblage which aggregated near the cage. The pattern of scavenger visits suggests avoidance among taxa and a succession of scavengers. Macrourids, a dominant abyssal scavenger, either did not respond to the death of their congener or possibly avoided the area. Lack of a response by macrourids may be due to (1) avoidance of sites of dead or dying congeners, (2) high sensitivity to ocean acidification, (3) low nutritional value or weaker odor plumes from carcasses of abyssal versus shallow-water taxa, or (4) rapid departure from sites where a carcass is inaccessible. Camera systems were not deployed in view of carcasses at control sites (away from CO 2 pools) during each experiment, and we therefore cannot exclude the possibility that the pattern of scavenger visits was influenced by elevated carbon dioxide levels.KEY WORDS: Food fall · Behavior · Macrouridae · Coryphaenoides armatus · Zoarcidae · Pachycara bulbiceps · Octopodidae · Benthoctopus sp. Resale or republication not permitted without written consent of the publisher OPEN PEN ACCESS CCESS

Baited-camera observations of deep-sea megafaunal scavenger ecology on the California slope

“…Lampitt et al (1983) used C. armatus as bait on the North Atlantic abyssal plain and noted very few rattails but many lysianassid amphipods and liparid fishes. Barry & Drazen (2007) observed similar aversion of C. armatus to a dead conspecific and hypothesized that macrourids avoid dead congeners or conspecifics because they may indicate dangerous conditions. It is also interesting that C. filifer, the other macrourid observed at 3000 m, had a marginally lower n max and higher first arrival time when C. armatus was used as bait.…”

“…It follows that scavenger response to baited experiments should be influenced by the type of bait being used, which for the most part has consisted of scombroid fishes (Priede et al 1990, Henriques et al 2002, Yeh & Drazen 2009). Barry & Drazen (2007) made opportunistic observations on the effect of introducing macrourid carrion on scavenger behavior when individuals of Coryphaenoides armatus died during caged experiments. Numbers of Pachycara sp.…”

Scavenging interactions between the arrow tooth eel Synaphobranchus kaupii and the Portuguese dogfish Centroscymnus coelolepis

“…non‐lethal tail cropping between fishes (Campbell et al , 1980), squat lobsters avoiding predatory octopods (Kemp et al , 2006) and decapods avoiding fishes (Thurston et al , 1995). There is even evidence to suggest avoidance of fishes if a conspecific is used as bait (Barry & Drazen, 2007). These deviations, no matter how slight, have the potential to skew the estimated effects of physical and behavioural variables such as fish arrival rates and staying times, and therefore ultimately understanding the true feeding strategy of deep‐sea scavengers.…”

The National Geographic Society Deep-Sea Camera System: A Low-Cost Remote Video Survey Instrument to Advance Biodiversity Observation in the Deep Ocean

“…Therefore, the specific bait type will vary among sampling campaigns specific to the region (Langlois et al, 2018). However, the use of deep-sea fish as bait may cause avoidance in conspecifics (Barry and Drazen, 2007), so surface-dwelling or pelagic fishes of the region should be used.…”