Deepwater snappers and groupers support significant fisheries in Hawai’i, the U.S. Pacific Territories and the rest of the South Pacific and Indian Oceans. They include the Pristipomoides (opakapaka, gindai, kalekale, goldeye kalekale), Etelis (onaga, ehu) and Hyporthodus (hapu’upu’u, eight-bar grouper) (Figure 1). Primarily due to the great depths these species inhabit, important life history estimates (age, growth, longevity, size-at-maturity) are notoriously difficult to determine at best and were at one point, thought impossible to determine. However, a series of workshops have challenged that assertion and progressed life history information about these species.
Several members of the Life History Program participated in the 3rd Deepwater Snapper and Grouper Life History Workshop held at the Western Australia Department of Fisheries in Hillarys, WA (Figure 2 and 3). The primary purpose of these workshops is to bring together researchers from throughout the Pacific and Indian Oceans who work on this unique set of species. Rather than sitting and listening to lectures all day, these workshops were structured with topical discussions in the morning and hands-on work in the afternoon.
The first workshop was held in New Caledonia and focused on data. The second workshop was held at the IRC in May 2015 with an overarching theme of advancing otolith preparation, interpretation, and standardization. The themes of the 2016 workshop were sharing recent advances in otolith preparation and estimating trait values influencing population dynamics (especially mortality) from length and age data.
A variety of guest speakers presented their theories and tools used to advance knowledge of deepwater snappers and groupers and generated lively discussions. These included Joyce Ong from The University of Western Australia Oceans Institute (dendrochronology), Euan Harvey and Claire Wellington (BRUVS – Baited Remote Underwater Video Stations) and Mike Bunce (environmental DNA) from Curtin University.
During one of the afternoon sessions, snapper otoliths (used to determine fish age, Figure 4), collected during the 2016 Samoa Archipelago Fisheries Research Cruise (see SE16-01: Bottomfishing for samples at https://pifscblog.wordpress.com/2016/03/30/se16-01-bottomfishing-for-samples/), were examined by researchers from PIFSC and Western Australia Department of Fisheries and used to estimate growth rates (Figure 5). Another breakout group, consisting of stock assessment scientists from PIFSC and Western Australia, built mathematical models that used the age information and the estimated growth rates to estimate natural and fishing morality (Figure 6). These two extremely important pieces of information help scientists assess stock status. Preliminary results indicated that the fish otoliths were prepared properly and the established fish ageing protocols were acceptable to produce reliable fish age estimates and that the mortality mathematical models were behaving properly. This combination will result in robust life history and population dynamic information for not only this snapper species but the methodologies can be applied to other deepwater snapper and grouper species as well.
Plans are already underway to capitalize on the momentum generated at this workshop. Details of the 4th Workshop are already being discussed. Stay tuned for a variety of reports from the LHP and their collaborators (WA Fisheries, SPC, TNC in Indonesia) including the life history of several Pristipomoides, Etelis and Hyporthodus species, suggested harvest strategies for deepwater species, and comparisons of different methods to estimate mortality based on the amount of available life history information for a given species. This highly successful workshop and the planned research and papers will significantly reduce the knowledge gap of these important fishes and facilitate sustainable management.