Reproductive Characteristics and Mortality of Female Giant Grenadiers in the Northern Pacific Ocean

C J Rodgveller,D M Clausen,J J Nagler,C Hutchinson

doi:10.1577/c09-028.1

Abstract

AbstractGiant grenadiersAlbatrossia pectoralisare caught as bycatch in deep‐sea commercial fisheries in relatively large numbers. The population appears to be stable, although there is no directed fishery, catch limits, or reporting requirements. The purpose of our study was to describe and quantify the reproductive life history characteristics and natural mortality of female giant grenadiers. During the summers of 2004 and 2006, a total of 338 specimens were collected from the Gulf of Alaska. Every phase of reproductive development was found, suggesting a protracted annual spawning season. An ovarian wall thickness technique was used to successfully place 31% (n= 24) of the fish with an unknown maturity status into a known category. Female age at 50% maturity was 22.9 years, and preanal fin length at 50% maturity was 26 cm. Total fecundity ranged from 35,000 to 231,000 oocytes (mean = 106,761), with a mean mature oocyte diameter of 1.26 mm. We developed a new technique for preparing otoliths for age determination by grinding off the distal surface to elucidate the growth zones; age ranged from 14 to 58 years. Estimates of natural female mortality ranged from 0.052 to 0.079 and estimates of total female mortality from 0.061 to 0.149. This life history information will be essential for future management of giant grenadier populations in the North Pacific Ocean.

Highlights

National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Center, 7600 Sand Point Way N.E., Seattle, Washington 98115, USA
There has never been a directed fishery for giant grenadiers in the Gulf of Alaska (GOA), but they are frequently taken as bycatch in the sablefish Anoplopoma fimbria longline fishery
A study of giant grenadier age and growth off the U.S West Coast, GOA, and Aleutian Islands found that age ranged from 13 to 56 years based on radiometric aging and otolith readings (Burton 1999)

Summary

Introduction

National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Center, 7600 Sand Point Way N.E., Seattle, Washington 98115, USA. Estimates of natural female mortality ranged from 0.052 to 0.079 and estimates of total female mortality from 0.061 to 0.149 This life history information will be essential for future management of giant grenadier populations in the North Pacific Ocean. There are no catch limits or reporting requirements for giant grenadiers Because they are relatively large (.14 kg), numerous, and widespread, they have economic potential, like other grenadiers that have been commercially exploited, such as roughhead grenadier Macrourus berglax (Fossen et al 2003), roundnose Coryphaenoides rupestris (Atkinson 1995), and Pacific Coryphaenoides acrolepis (Clausen 2008). Giant grenadier catch and distribution have been described off Alaska (Clausen 2008), Kamchatka, and the northern Kuril Islands (Orlov and Tokranov 2008). Tuponogov et al (2008) described the distribution of giant grenadiers from the RODGVELLER ET AL

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