Fig 1.
Research strata within the vicinity of Heard Island and McDonald Islands strata covering the distribution of grey rockcod are Rockcod Grounds South, Pike & Discovery Banks and Shell Bank, blue lines indicate strata boundaries, bathymetry data obtained from Geoscience Australia [30].
Fig 2.
Log mean catch (kg) of grey rockcod (Lepidonotothen squamifrons) caught within research surveys (1990–2014) within the vicinity of Heard Island and McDonald Islands (green) plotted at a 0.1° x 0.1° resolution.
Pink lines indicate marine protected areas as defined in 2014 [39], bathymetry data obtained from Geoscience Australia [30].
Fig 3.
Length weight relationship for grey rockcod (Lepidonotothen squamifrons) across three locations within the vicinity of Heard Island and McDonald Islands; Rockcod Ground South (red), Shell Bank (black) and Pike & Discovery Banks (blue) 1990–2014.
Table 1.
Ranges of combined years body length and weight and estimates of parameters a and b of the length-weight relationship of Lepidonotothen squamifrons using data collected from three locations within the vicinity of Heard Island and McDonald Islands during research surveys.
Fig 4.
Comparison of estimated weight at 300 mm and 400 mm for grey rockcod (Lepidonotothen squamifrons) through various years and all years combined across three locations within the vicinity of Heard Island and McDonald Islands; Rockcod Ground South (A), Pike & Discovery Banks (B) and Shell Bank (C).
Fig 5.
Length density distribution for grey rockcod (Lepidonotothen squamifrons) in the vicinity of Heard Island and McDonald Islands, and all years (1990–2014); Rockcod Ground South (red), Shell Bank (black) and Pike & Discovery Banks (blue). Dotted lines indicate size of 50% sexual maturity for both sexes in Rockcod Ground South (red) and Pike & Discovery Banks (blue), 50% sexual maturity in Shell Bank (black) is shown for females (dashed) and males (dotted)(see Fig 7).
Fig 6.
Comparison of annual fish density with weight at a length of 400 mm within the vicinity of Heard Island and McDonald Islands; Pike & Discovery Banks (blue), Shell Bank (black) and Rockcod Ground South (red) for grey rockcod (Lepidonotothen squamifrons).
Table 2.
Density estimates (fish n/km2) of grey rockcod (Lepidonotothen squamifrons) from three locations within the vicinity of Heard Island and McDonald Islands.
Standard errors are shown in parentheses.
Fig 7.
Maturity rates by length for male and female grey rockcod (Lepidonotothen squamifrons) caught in three locations within the vicinity of Heard Island and McDonald Islands.
Fig 8.
Box and whisker plots of age class distributions obtained from otoliths of grey rockcod (Lepidonotothen squamifrons) across locations within the vicinity of Heard Island and McDonald Islands.
Note, locations with less than 10 samples have been grouped as ‘other’.
Fig 9.
Varying parameter von Bertalanffy growth curves for grey rockcod (Lepidonotothen squamifrons) at Shell Bank (dashed lines and grey ▲ n = 549) and Pike & Discovery Banks (solid lines and blue ▼ n = 114) within the vicinity of Heard Island and McDonald Islands.
Note: pink and green dashed lines sit on top of each other.
Table 3.
Comparison of von Bertalanffy model parameters of grey rockcod (Lepidonotothen squamifrons) growth curves for Shell Bank and Pike & Discovery Banks within the vicinity of Heard Island and McDonald Islands compared using Akaike Information Criterion (AIC).
Fig 10.
Potential connectivity pathways between three geographical populations of grey rockcod (Lepidonotothen squamifrons) within the vicinity of Heard Island and McDonald Islands (green).
Scenarios indicate recruitment sources (blue and red arrows) and recruitment sinks (blue, red, black arrows at Shell Bank). Note light blue outlined arrows indicate pelagic recruits transported by oceanographic features adapted form Park et al., [60], bathymetry data obtained from Geoscience Australia [30].