What can volunteer angler tagging data tell us about the status of the Giant Trevally (ulua aukea) Caranx ignobilis fishery in Hawaii: revisiting data collected during Hawaii’s Ulua and Papio Tagging Project 2000-2016

Giant Trevally (ulua aukea) Caranx ignobilis is one of the most highly prized and frequently
targeted nearshore species. However, there is very little information on its current status in
Hawaiian waters. This study uses mark-recapture data collected as part of recreational angler
tagging program conducted by the Hawaii Department of Land and Natural Resources-Division
of Aquatic Resources during 2000-2012. Mark-recapture data were used to estimate von
Bertalanffy growth curve parameters and survivorship. Growth curves generated from the markrecapture
data suggested that Giant Trevally from the main Hawaiian Islands may be growing
faster and reach a smaller maximum size than individuals in the Northwest Hawaiian Islands, but
there are a number of issues rendering this conclusion uncertain. The survivorship of Giant
Trevally was positively associated with age, in part due to ontogenetic habitat shifts that result in
older fish moving to offshore habitats where they are less vulnerable to anglers. When compared
to stock assessments performed using commercial landings data and fisheries-independent visual
surveys, the mark-recapture data produced similar estimates for the average length of exploited
fish, a metric highly negatively correlated to fishing mortality. These results emphasize the need
for additional information on the biology of Giant Trevally in Hawaiian waters and suggest that
the data collected from this recreational angler tagging program may be useful to generate
reliable estimates of mortality for stock assessment purposes.