Jackass Morwong Biology


SpeciesNemadactylus macropterus
Common NameJackass Morwong
HabitatExposed sand and silt
Depth5 – 400 m (Edgar, 2008)
DistributionCentral Queensland to southern Western Australia, around Tasmania, New Zealand, southern Africa, South America (Edgar, 2008)
DietPolychaetes, crustaceans, molluscs, echinoderms (Godfriaux, 1974)
Stock StructureExistence of at least three sub-populations: Tasmania, New South Wales/Victoria, Great Australian Bight; no genetic variation in southern Australia indicates larval mixing (Grewe et al., 1994; Elliott and Ward, 1994; Richardson, 1982; Thresher et al., 1992).
M (Natural Mortality)0.10 (New Zealand population) (Parker and Fu, 2011)
Maximum Age (years)50 (Edgar, 2008)
Maximum Length (total length; cm)70 (Kailola et al., 1993)
Maximum Weight (g)2900 (Kailola et al., 1993)
Female K (von Bertalanffy growth parameter)0.36 (Jordan, 2001a)
Male K (von Bertalanffy growth parameter)0.42
Female t0 (age (years) when length = 0)-0.07
Male t0 (age (years) when length = 0)0.15
Female L∞ (asymptotic von Bertalanffy length (total length; cm))38.4
Male L∞ (asymptotic von Bertalanffy length (total length; cm))36.2
Size at Maturity (length (total length; cm) at sexual maturity)25
Age at Maturity (years)3 (Edgar, 2008)
Spawning SeasonFebruary – June
Spawning LocationAt least two spawning areas: northern (probably southern New South Wales and eastern Victoria), southern (probably western and southern Tasmania) (Bruce et al., 2001a; Lyle and Ford, 1993)
RecruitmentNo-stock recruitment relationship established
Early Life HistoryPlanktonic larval stage 7 – 10 months; larvae drift ≤ 30 mm drift with current on surface ≤ 250 km east of Tasmania; settlement at 7 – 9 cm length; juveniles live near shallow reefs (Francis, 2001; Bruce et al., 2001a; Kailola et al., 1993)
Gillnet Post Release SurvivalModerate: 52% (Lyle et al., 2014)