Essential fish habitat and life history assessment of commercially important herbivores in Pohnpei, Micronesia, to enhance MPA effectiveness
University of Guam
Type Period Note:
Final Report, 2/1/2011 - 8/31/2012
"A total of 516 Naso lituratus were sampled to examine spatial habitat use and characterize the reproductive biology and age and growth, respectively, for this species. Similarly, 22 Naso unicornis were taken from the field and 302 from markets to estimate these same parameters. Based on findings, both N. lituratus and N. unicornis are gonochostic species that spawn monthly throughout the year. For N. lituratus, a peak in reproductive activity was indicated from January-July, suggesting that optimal times for temporal management to protect reproductive adults be instituted within this period. For N. unicornis, GSI values did not provide a clear indication of spawning seasonality. Nonetheless, female with hydrated oocytes were observed from May-November. Reproductive activities for either species did not appear to conform to a specific lunar period. For both species, there was a significant sex-specific difference in age, with females older than males. Male N. lituratus matured at 1 yr old (range=1-13 years), while mature females appeared at Age 2 (range=1-13 years). For N. unicornis, females ranged from 1-16 years, while males were 1-14 years old, with no sex-specific difference in age. Mature N. unicornis appeared in samples at Age 1 for both sexes. For N. unicornis, samples appeared in markets well below their reported maximum lengths. For the acoustic tagging component, some variability was noted in movement patterns (as receiver detections) that suggest differences in their vulnerability to fishing. Three of the 13 N. unicornis were recaptured by the fishery, while none of the 10 N. lituratus were taken. Patterns of movement showed most N. lituratus with reliable detection patterns to reside primarily within the MPA boundaries where they were first sampled, whereas N. unicornis were shown to move up to at least 4 km outside the MPA, with evidence of fisheries mortality. Based on these combined assessments, both species could benefit from management improvements. For both species, temporal fishing restrictions within the spawning season are recommended, with a recommended period from June-August for both species. Such a ban would fall outside the current grouper sales ban period. In addition, N. unicornis could benefit from a combination of a size limit for the fishery and an expanded marine protected area."
NOAA CRCP grant NA09NMF4630108 Socioeconomic Assessment and Resource Evaluation