CSIRO Publishing blank image blank image blank image blank imageBooksblank image blank image blank image blank imageJournalsblank image blank image blank image blank imageAbout Usblank image blank image blank image blank imageShopping Cartblank image blank image blank image You are here: Journals > Marine & Freshwater Research   
Marine & Freshwater Research
Journal Banner
  Advances in the Aquatic Sciences
blank image Search
blank image blank image
blank image
  Advanced Search

Journal Home
About the Journal
Editorial Board
Online Early
Current Issue
Just Accepted
All Issues
Special Issues
Research Fronts
Sample Issue
For Authors
General Information
Instructions to Authors
Submit Article
Open Access
For Referees
General Information
Review Article
Referee Guidelines
Annual Referee Index
For Subscribers
Subscription Prices
Customer Service
Print Publication Dates

blue arrow e-Alerts
blank image
Subscribe to our Email Alert or RSS feeds for the latest journal papers.

red arrow Connect with us
blank image
facebook twitter youtube


Article << Previous     |         Contents Vol 43(5)

Growth and demography of the Pacific Angle Shark (Squatina californica), based upon tag returns off California

GM Cailliet, HF Mollet, GG Pittenger, D Bedford and LJ Natanson

Australian Journal of Marine and Freshwater Research 43(5) 1313 - 1330
Published: 1992


Knowledge of the age, growth and demography of an organism can be quite useful for managing its fishery. However, for many elasmobranch species, no valid estimates of age, growth and therefore age-specific mortality and natality rates are available. Thus, even though the distribution, abundance, habits and reproduction of a population may be known, no reliable estimates of population growth are possible. As a result, detailed demographic analysis has been completed for only a few shark species (e.g. the California leopard shark, Triakis semlfasciata). All age-determination techniques attempted for the Pacific angel shark (Squatina californica) have met with difficulties. Recently, however, we have accumulated data on 69 tag-recaptures and have used this information to model a von Bertalanffy growth function (VBGF) to predict the growth of this commercially exploited shark species. We performed a demographic analysis of this species, which yielded a net reproductive rate (R0) of 2.25, a generation time (G) of 14.5 years, and an estimate of the instantaneous population growth coefficient (r) of 0.056 year-1, assuming that only natural mortality (M) was occurring, estimated to be 0.2 year-1. When reasonable estimates of fishing mortality (F) are included in the survivorship function, Ro and r are reduced considerably. Presently, Pacific angel sharks first enter the fishery at the same size and age at which they first reproduce. Until accurate estimates of M and Fare available, it would be prudent to set a size limit considerably above the size at first reproduction to protect the Pacific angel shark in California.

Full text doi:10.1071/MF9921313

© CSIRO 1992

blank image
Subscriber Login

PDF (937 KB) $25
 Export Citation
Legal & Privacy | Contact Us | Help


© CSIRO 1996-2014