Age, growth, and commercial landings of yellowtail scad (Trachurus novaezelandiae) and blue mackerel (Scomber australasicus) off the coast of New South Wales, Australia

Size and age compositions of yellowtail scad (Trachurus novaezelandiae Rich ardson 1843) and blue mackerel (Scomber australasicus Cuvier 1832) were stu died in the inshore purse-seine fishery off the coast of New South Wales, A ustralia. Ages were assigned by counting annual marks in otoliths for both species. Sampling from two regions showed no geographical differences in th e age compositions of catches for either species. The fishery for yellowtai l scad was based on 2- and 3-year-old fish, but with significant numbers of fish up to 11 years. Seventy percent of the fishery for blue mackerel was based on fish aged 1 year, with the majority of the rest being in their fir st or third years. Maximum ages recorded in this study were 14 years for ye llowtail. scad and 7 years for blue mackerel. We found no major differences in the sizes of blue mackerel landed in either region sampled, but yellowt ail. scad were larger in the northern region than in the southern. Growth r ates of blue mackerel were the same from both regions, but yellowtail scad sampled grew significantly faster in the northern region. The fishery for y ellowtail scad off New South Wales is currently based on younger and smalle r fish than other trachurid fisheries around the world. This, together with the observed spatial variation in growth and population structure, suggest s that the fishery for yellowtail scad in New South Wales should be careful ly monitored.