Demography of parrotfish: age, size and reproductive variables

Barba, Jacquelyn (2010) Demography of parrotfish: age, size and reproductive variables. Masters (Research) thesis, James Cook University.

PDF (Thesis)
Download (4MB)
View at Publisher Website:


This thesis examined variation in demography and life history traits of scarine labrids across broad (across 27˚ latitude) and local (10-100's of kilometre) scales, as well as to what extent fishing had an influence. Eight parrotfish species were initially examined at a local level (GBR) to interpret differences in growth using an age-based approach. From this preliminary analysis parrotfish were then classified into two groups according to their growth pattern, indeterminate and asymptotic. This analysis revealed growth to be associated with other essential life history traits such as: growth, longevity and maturity. Next, a more detailed look was taken for five species on the GBR to examine variation at a local scale. For large parrotfish species, Chlorurus microrhinos, no differences in growth and life span were found between populations from mid and outer shelf reefs. However, for all small parrotfish species, populations from outer reefs had significantly reduced growth rates and shorter life spans. These results suggested that there will be short term changes in growth patterns depending on the habitat in which individuals will recruit into. Comparison of reproductive parameters, age and size at maturation and sex change, revealed earlier maturation and sexual transformation occurred in populations from outer shelf reefs. Timing of both maturation and sex change was not only driven by how long an individual lived or how big they are, but by reproductive behavior. Two species, Chlorurus sordidus and Scarus psittacus were then used to address in more detail other drivers on life history variation. First, the demography and life history of both species was compared at a broad (geographic) scale between Guam and the GBR. Broad scale variation is generally explained by the temperature size rule, however in both species growth, life span and reproductive parameters were reduced at Guam locations (higher latitudes) compared to GBR locations (lower latitudes). Second, the potential impacts of fishing on demographic characteristics of both species were examined. Populations of both C. sordidus and S. psittacus from fished areas represented reduced growth, shorter life spans, earlier maturation and earlier sex reversal. However, this variation was minimal when compared variation in similar traits occurring at a local scale.

Item ID: 26682
Item Type: Thesis (Masters (Research))
Keywords: Chlorurus microrhinos; Chlorurus sordidus; coral reef fish; demography; fishing; GBR; Great Barrier Reef; growth; Guam; impacts of fishing; life cycle; life histories; life history; life span; longevity; maturation; Northern Australia; parrot fish; parrot fishes; parrotfishes; populations; reproduction; Scaridae; scarine labrids; Scarus psittacus; Great Barrier Reef; GBR
Date Deposited: 06 May 2013 00:31
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 40%
07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070403 Fisheries Management @ 20%
06 BIOLOGICAL SCIENCES > 0603 Evolutionary Biology > 060308 Life Histories @ 40%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8302 Fisheries - Wild Caught > 830204 Wild Caught Fin Fish (excl. Tuna) @ 33%
96 ENVIRONMENT > 9699 Other Environment > 969902 Marine Oceanic Processes (excl. Climate Related) @ 33%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 34%
Downloads: Total: 1004
Last 12 Months: 30
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page