Studies on the Biology and Ecology of Opah (Lampris guttatus) and Monchong (Taractichthys steindachneri) in the North Pacific 1 2 1
TMOS D A PHE AN R Michael P. Seki , Donald R. Hawn and Robert Nishimoto I C C I A N D A M E I C N 1 O I S
L T
A R
N A
T
O
I
I
O
T N
A Pacific Islands Fisheries Science Center, National Marine Fisheries Service, 2570 Dole Street, Honolulu, HI 96822 N
U . E S C .D R E E 2 PA M RT OM MENT OF C Joint Institute for Marine and Atmospheric Research, 2570 Dole Street, Honolulu, HI 96822
ABSTRACT Two pelagic species incidentally caught by Hawaii-based longliners targeting bigeye tuna in the North Pacific are the opah, Lampris guttatus, and monchong, Taractichthys steindachneri. Particularly valued by the restaurant trade in Hawaii, these exotic, deep-water fishes are generally harvested in small, but nevertheless significant, quantities. Since neither are targeted species, these fishes have historically been poorly studied and as a result available information pertaining to the biology and ecology are virtually nonexistent. A study to fill these gaps in our knowledge was undertaken and presented here are some of the highlights from the going work.
The primary objective of the study is to investigate and define some of the fundamental life history and ecological characteristics of these important incidentally caught species through a combination of comprehensive shoreside data and biological sample collection, analysis and merging of industry (NMFS observer and logbook, North Pacific driftnet, auction), research, and environmental datasets, and capture depth information collected from vessels of opportunity. When completed, the study will have produced (1) comprehensive seasonal and where possible, interannual biometric summaries and relationships (e.g. length-weight, sex ratio, etc.), (2) preliminary determination of age structure and reproductive parameters (size and age at maturity, fecundity, spawning season, gonadosomatic index), and elucidate distribution patterns, preferred habitat, faunal associations, and trophic relationships for both "specific" resources. Results from this study will provide fishery managers with new and much needed fundamental biological information that will help refine a precautionary reference point and provide insights into factors that enhance and reduce the incidental take of these species.
male female
“ deep, abrupt angle” “gradual rounding”
“thick, concave” “narrow, convex”
Opah (Lampris guttatus) female male Monchong or pomfret harvested in Hawaii-bases fisheries are Pomfret (Taractichthys steindachneri) composed principally of two species: the sickle pomfret A big breakthrough in the early stages of the study (Taractichthys steindachneri) and the lustrous pomfret (Eumegistus was the discovery that opah exhibit sexual illustris) and distinction between the two can be readily dimorphism that enables the determination of a fish's distinguished by diagnostic systematic characters. A comprehensive gender without cutting into the peritoneal cavity to shore-based sampling program at the United Fishing Agency (i.e., examine the gonads for the determination of sex. This local fish auction) from 1984 through 2000 is used to monitor determination has allowed substantially more data landing and catch composition. collection both shoreside and in the field. Complementary ongoing studies of opah movement A comprehensive shore-based biological sampling program NMFS-UFA monitoring, 1984-2000 using satellite archival tags have benefited by this has been set up at three selected fish buyers/dealers to obtain Species No. (%) Lbs. (%) finding in allowing us to examine the movements of the metrics (length, weight, and sex) and samples (ovaries, these fish by sex. The U.S. west coast observer otoliths, and stomachs) required to conduct a comprehensive E. illustris 1,020 (2.1%) 14,526 (2.0%) program based out of Long Beach, CA as well as the biological and ecological assessment. Hawaii-based observer program have also recently T. steindachneri 46,786 (97.9%) 717,174 (98.0%) incorporated the external gender determination into **recent confirmation of mixed catch on set – mixed schools (?) their monitoring program.
Hook Timers Monchong
The assessment of spatial distribution patterns, preferred habitat, faunal associations, and trophic relationships involves Time-Depth Recorders the analysis and merging of industry (NMFS observer and Attaching time-depth-temperature recorders (TDRs) and logbook, North Pacific driftnet, auction), research, and hook-timers to sections of the longline have been found Map showing points of release (circles) and points of environmental datasets, and capture depth information useful in estimating depth and time of capture. During pop-up (arrow tips) for seven males and seven females released collected from vessels of opportunity. For example, this the opah-monchong project, a total of 590 TDRs profiles from pelagic longline gear in the central North Pacific and figure shows incidental catch rates of opah in the now defunct have been acquired for 171 baskets of gear from 45 equipped with pop-up satellite archival tags during four research Asian high-seas surface driftnet fisheries (red circles) and the longline sets and over 4 trips. On these instrumented trips in 2002 and 2003. Days at liberty represented in italics. Hawaii-based longline fishery (blue circles). In general, sections, a total of 70 fish have been captured including The figure above shows opah landings at the UFA smaller individuals are taken at higher latitudes ranging from 18 monchong and 4 opah. during 2000-2001. Dealer price/weight data 30 to 107 cm with a mean of 64 cm; large fish in the longline shows smaller fish landed and lower prices in the fishery operating in the subtropics. Fall for 2000 and 2001.