Opah Distribution

In 2011, scientists at SWFSC began opportunistically tagging opah off the coast of California with satellite tags. These tags track fish movement and depth and provide information on habitat utilization and migrations that are important in understanding the basic biology of the species and can have impacts on future population assessments and management decisions. Historical catch data may also provide insight into opah movements and can be used to understand correlations between opah catch and abundance with changes in sea surface conditions such as El Niño and La Niña


NMFS biologists keep water flowing through the gills of an opah they tagged off Southern California. An opah outfitted with a satellite tag is released off a SWFSC research cruise in Southern California.



Migration and Diving Behavior

Satellite tag used to tag opah (Lampris guttatus) in the California Current. These tags are programmed to record water depth, temperature, and light levels, helping scientists gain insight into the diving behaviors of opah. 
Image credit Liana Heberer.Between October 2011- November 2012, eight opah were tagged during NOAA research surveys with Wildlife Computers The previous link is a link to Non-Federal government web site. Click to review NOAA Fisheries Disclaimer  Mk10-PAT (pop-off archival tag) that were programmed to record water depth, temperature, and light levels for up to 240 days. This information allows researchers to later reconstruct opah movement over time and gain insight into their diving behaviors. Four of the deployments were at liberty for the allotted 240 days and two tags released early (4 days and 26 days) due to a mortality and predation event, respectively.  


Release locations (green markers) and recapture locations (red markers) are shown for eight opah that were satellite tagged in the Southern California Bight. One of the tagged opah was at liberty for the full 240 days and traveled 623 miles down the coast of the Baja Peninsula.



One of the tagged opah that was at liberty for the full 240 days traveled 623 miles down the coast of the Baja Peninsula before the tag popped off. This fish occupied depths from 20-300 meters during the day and stayed in waters shallower than 100 meters at night. This diel migration pattern is similar to other pelagic predators that exploit prey associated with the deep scattering layer. Opah vertical movements are likely associated with following prey such as squid and  barracudinas, a small elongated fish of up to 50 centimeters. The barracudina is a notable mid-water prey item for large fishes such as tunas, swordfish, bigeye thresher shark and, evidently, opah. Read more about opah foraging ecology.

           

   



Diving behavior can be inferred from depth vs. time patterns produced by satellite tag data. This opah, Tag #60648, inhabited deeper waters during the day and shallower waters at night.




Diving behavior can be inferred from depth versus time patterns produced by satellite tag data, and this same opah that traveled for 240 days appeared to spend time in deeper waters during the day and shallower waters at night. It was also observed to dive between depths of 0-250 meters during warmer months (June-October) and between 50-220 meters during colder months (November-March). This switch in diving behavior suggests seasonal southward movement out of the California Current into warmer waters of Baja California, Mexico. 









                                  


Historical Catch Data


Recreational catch vs. El Niño Southern Oscillation (ENSO) eventsCalifornia Drift Gillnet (CADGN) fishery catch per set vs. El Niño Southern Oscillation (ENSO) events                                                                                                             

                           Click here to view larger images: Historical catch of opah in the Southern California Bight-SWFSC


An increase in availability of opah on NOAA research cruises prompted SWFSC to look at historical catch data for opah in the Southern California Bight (SCB). Preliminary analysis of the California Drift Gillnet (CADGN) Fishery Observer Database suggests that opah catch has been increasing in recent years. Opah catch rates from 1990 to 2009 averaged 2.31 opah per set with peak catch rates observed during 1997 (4.44), 2007 (3.41), and 2009 (4.40). Comparatively, recreational fishing logbooks reported an average of 5.44 opah per year with peak catch occurring in 2003 with 35 opah. While further analysis including changes to the CADGN fishery must be taken into account, both commercial and recreational catch of opah in the SCB appears to be increasing over the last decade. Given that people fishing today have better gear and advanced electronics, opah may simply be increasing in availability to recreational anglers. A more detailed examination of trophic overlap between opah and other local predators will help to identify whether their apparent increase in abundance is related to a reduction in competition from top predators, an increase in their population size, environmental variability, or a change in their behavior and migration patterns. Comparison of opah catch rates and the Oceanic Niño Index (ONI) suggest correlations between catch rates and conditions such as El Niño and La Niña. 


Last modified: 12/8/2015