Age, growth and maturity for two highly targeted jack species: Caranx ignobilis and Caranx melampygus

Abstract

This study provides growth rate, longevity and maturity estimates for the two important species of jack in Hawaiʻi: ulua aukea/giant trevally Caranx ignobilis and omilu/bluefin trevally Caranx melampygus. Maximum observed ages for C. ignobilis and C. melampygus were 31 years and 24 years, respectively. Combined sex von Bertalanffy growth parameter values for C. ignobilis and C. melampygus were as follows: L∞ = 1064 mm and K = 0.18 year−1; and L∞ = 718 mm and K = 0.20 year−1, respectively. Female size at maturity was significantly greater than males for both C. ignobilis and C. melampygus. Size and age at maturity for C. ignobilis was 594 mm and 4.4 years for females and 465 mm and 2.8 years for males. Size and age at maturity for C. melampygus was 372 mm and 4.1 years for females and 329 mm and 2.9 years for males. This study provides the first robust demographic data for both of these highly prized and ecologically important predatory species in Hawaiʻi, which can be used for future assessments or management.

Working with community fishers to determine the spawning seasonality of two commonly targeted jack species

“…The state of Hawai’i imposed a minimum capture size of 25.4 cm FL (10 in) for both Giant and Bluefin trevally; however, neither species has had an opportunity to reproduce at that size (Hawaii Division of Land and Natural Resources 2010; Pardee et al. 2021). Due to the popularity of Giant and Bluefin trevally among the people of Hawai’i, there has been concern about declining populations across the state (Sudekum et al.…”

“…The jack fishery represents the most popular noncommercial fishery in Hawai'i, with the Giant Trevally (known in Hawai'i as ulua aukea) Caranx ignobilis and the Bluefin Trevally (known in Hawai'i as 'ōmilu) Caranx melampygus representing the most commonly targeted jack species (Tagawa and Tam 2006). Both species live over 20 years and reach maturity at around 4 years for females and 2.5 years for males, which corresponds to female Giant Trevally reaching maturity at 59 cm fork length (FL) and female Bluefin Trevally reaching maturity at 37 cm FL (Pardee et al 2021). The state of Hawai'i imposed a minimum capture size of 25.4 cm FL (10 in) for both Giant and Bluefin trevally; however, neither species has had an opportunity to reproduce at that size (Hawaii Division of Land and Natural Resources 2010; Pardee et al 2021).…”

“…Both species live over 20 years and reach maturity at around 4 years for females and 2.5 years for males, which corresponds to female Giant Trevally reaching maturity at 59 cm fork length (FL) and female Bluefin Trevally reaching maturity at 37 cm FL (Pardee et al 2021). The state of Hawai'i imposed a minimum capture size of 25.4 cm FL (10 in) for both Giant and Bluefin trevally; however, neither species has had an opportunity to reproduce at that size (Hawaii Division of Land and Natural Resources 2010; Pardee et al 2021). Due to the popularity of Giant and Bluefin trevally among the people of Hawai'i, there has been concern about declining populations across the state (Sudekum et al 1991;Gaffney 2000;Friedlander and DeMartini 2002).…”

“…The two largest projects are the bonefish/ʻōʻio (Roundjaw Bonefish Albula glossodonta and Longjaw Bonefish A. virgata) and jack/ulua tagging projects that are run by the state of Hawai'i, in which volunteer fishers catch, tag, and release fish after gathering length and location data (Tagawa and Tam 2006;Kamikawa et al 2015). Other community collaboration projects have involved fishers collecting fish and gonad samples for age, maturity, and spawning season studies focused on important coral reef species throughout Hawai'i (Schemmel et al 2016;Schemmel and Friedlander 2017;Pardee et al 2021). One collaborative study used community-based monitoring to assess seasonal spawning peaks, lunar spawning cycles, and size at maturity for 10 reef fishes at four locations across the Hawaiian Islands (Schemmel et al 2016).…”

“…2016; Schemmel and Friedlander 2017; Pardee et al. 2021). One collaborative study used community‐based monitoring to assess seasonal spawning peaks, lunar spawning cycles, and size at maturity for 10 reef fishes at four locations across the Hawaiian Islands (Schemmel et al.…”