Pleuragramma antarcticum, has a circumpolar distribution in high Antarctic waters at depths to 700 meters. P. antarcticum has a complex life history. Eggs are spawned in sea areas along the major continental ice shelves during the austral spring. Larvae hatch (6-9 mm) by November-December in colder nearshore shelf areas. The onset of juvenile metamorphosis is believed to occur at lengths of 20-30 mm (2-4 years) and is completed by 36.8 mm. Benthopelagic adults (8-10 years old) return to the shelf to spawn.
Daily band widths apparently reflect the rate of fish growth. Antarctic fishes must be adapted to grow quickly during the short peak of regional primary productivity. The present study investigates regional differences in the early growth rates of P. antarcticum. Temporal and spatial variability in early growth rates are being examined using larval, juvenile and adult specimens from Marguerite Bay, Elephant Island, Weddell Sea, Prydz Bay, McMurdo Sound, and Bellingshausen Sea. Calculated growth rates for each location and year will be correlated with environmental parameters (e.g., sea-ice cover, water temperature and relative productivity) to evaluate the relationship between the environment and fish growth.
To date, 339 specimens have been analyzed. Fish standard lengths range from 10 mm to 185 mm and ages were estimated as 0.1 year to 25.6 years. Sagittal otoliths were removed from each specimen. Otolith diameter was measured to the nearest 0.01 mm. Back-calculations (e.g., predicting fish size given any otolith diameter) are dependent upon a strong relationship between the growth of the otolith and fish growth. The equation produced from the regression of pooled otolith dameter (mm) to pooled standard length (mm) is y=-9.2946e -2 + 1.3711e -2x (R2=0.961). Size at hatching and early growth rates will be determined. Further analyses will include enumeration of the daily growth increments using scanning electron microscopy. This information will be used for calculations of early growth rates at each location and year. Growth rates will then be correlated with environmental parameters to determine possible cause and effect.