Greymullet has a world wide distribution, occurring commonly along coasts,in estuaries, and in lower river systems between latitudes of 42^o N and 42^oS. Overseas and New Zealand tagging studies indicate that movementpatterns of adult grey mullet are complex. Some schools remain in onelocality, while others appear to be on the move almost continuously.Recorded movements of tagged grey mullet of 160 km within a few weeksof release are not uncommon.

 

Femalesgrow faster than males and attain a larger size. Both sexes mature at 3years of age at an average size of 33 cm fork length (FL) for males and35 cm FL for females. Maximum ages appear to be 12 to 14 years, withthe commercial fishery based primarily on 5 to 9 year old fish.

 

M was estimated from the equation M = loge100/maximumage, where maximum age is the age to which 1% of the populationsurvives in an unexploited stock. Using 15 years for the maximum ageresults in an estimate of M = 0.33. (Note: the maximum age of 15 yearswas obtained from an exploited population, so M is likely to be lessthan 0.33).

 

Greymullet commonly occur in schools, which generally become larger andmore prevalent in the spawning season. Spawning in northern New Zealandoccurs during November through February. Females are highly fecund andmay release up to 1 million eggs at a spawning. It is likely that greymullet spawn at sea, because running-ripe females have only been caughtoff coastal beaches or in offshore waters, and eggs and larvae are acomponent of the offshore coastal plankton at certain times of theyear. Small post-larval grey mullet occur seasonally in estuaries,which serve as nursery grounds for juveniles.

 

Adultgrey mullet typically feed on diatom algae and small invertebrateswhich are gulped along with surface scum or with detrital ooze andsifted by fine teeth and gill-rakers.