Opah Foraging Ecology

                        

                            Opah Gut Content Analysis (top) and various prey items found in opah stomachs (bottom)


                          

Since 2009, scientists from the Southwest Fisheries Science Center's Large Pelagics Lab have collected biological samples from opah caught incidentally during research surveys. Opah stomachs are collected during these research cruises aboard the F/V Ventura II and from carcasses also donated by recreational anglers from Southern California. To date, more than 130 stomachs have been collected and analyzed at the SWFSC, where prey items are identified, counted, weighed, and then ranked based on the Index of Relative Importance (IRI). 




Results of Gut Content Analysis (GCA) from opah collected in the California Current (CC)
Prey

% stomachs with each taxa  (% F)

 % total weight  (% W)

% total number (% N) Index of Relative Importance (IRI)
Gonatid Squid (Gonatidae 77.19 29.56 0.23 49.37
Humboldt Squid (Dosidicus gigas 29.82 32.45 0.03 20.79
Market Squid (Doryteuthis opalescens 49.12 14.88 0.16 15.86
Duckbill barracudina (Magnisudis atlantica) 47.37 4.45 0.03 4.55
Pacific Sardine (Sardinops sagax 8.77 0.73 0.00 0.14
Pacific Saury (Cololabis saira)   7.02 0.31 0.00 0.05
Jack Mackerel (Trachurus symmetricus)
1.75 0.47 0.00 0.02











Stomach content analyses suggest opah forage in both epipelagic (surface- 200 m) and mesopelagic (200-1000 m) zones, with a preference for mesopelagic prey. Squid made up more than 85% of the IRI, suggesting opah primarily feed on cephalopods. A total of 13 different squid species were found in opah stomachs, including the Humboldt squid (Dosidicus gigas), Market squid (Doryteuthis opalescens), and squids of the family Gonatidae. The remaining 5% of their diet is composed primarily of duckbill barracudina (Magnisudis atlantica), Pacific sardine (Sardinops sagax), Pacific saury (Cololabis saira), and jack mackerel (Trachurus symmetricus). Kelp was found in 30% of opah stomachs, indicating they may feed near floating kelp. One stomach also contained two fish associated with mud flats, Curlfin sole (Pleuronichthys decurrens) and juvenile cowcod (Sebastes levis), suggesting opah likely use the entire water column to forage and may be foraging in association with the benthos. 


The Large Pelagics Lab welcomes donated opah stomachs and carcasses from the California Current. To donate an opah carcass, stomach, or biological sample, contact Owyn Snodgrass at owyn.snodgrass@noaa.gov, or 858-234-2800.



                                                                                    Foraging Ecology and Occurrence of Opah (Lampris guttatus) in the Southern California Bight

                                                                        Read more about opah foraging ecology


Last modified: 12/8/2015