Abstract:
This study is based chiefly on pilchards from the Marlborough Sounds - Tasman Bay area of New Zealand. Most pilchards mature in their third or fourth year, at 135-139mm body length. Spawning occurs between November and February, and is more concentrated in Tasman Bay. Pilchard eggs are planktonic, with a single, small oil globule, wide perivitelline space, and a diameter range of 1.32 - 1.70mm. Eggs were taken in water of 14.7 - 20.9°C and. at depths of 0 – 30m. The incubation period is 56 - 58 hrs at 16.5°C. Pilchard larvae are 2.2 - 2.6mm long at hatching, and float in an inverted position at the surface. Yolk is absorbed when the larvae are about 3 days old and. 5.0 - 5.5mm long. Metamorphosis from postlarva to juvenile occurs at 35 - 40mm body length.
Pilchards attain a mean body length between 55 and 60mm in their first year. A scale ring is laid down in the second winter of life, and thereafter at about yearly intervals. In mature fish, a condition ring is formed soon after each yearly one. The mean body length at the time of ring formation is approximately 94, 122, 138, 151, 163, and 173mm for rings 1-6, respectively. Such lengths represent fish in their 2nd, 3rd, 4th, 5th, 6th, and 7th years of life. Pilchards attain a maximum body length of at least 213mm and a probable maximum age of 9 years. The growing season is spring and summer. The weight of the pilchard increases at a rate slightly greater than the cube of the length (W = .000003668L3.2399). New Zealand pilchards have a higher mean vertebral number (50.32) than Australian pilchards (49.72 - 50.08), showing that they are a distinct stock.
