Journal of the Marine Biological Association of India

Early developmental stages of the Indian mackerel Rastrelliger kanagurta (Cuvier) along the Kerala - Mangalore coast of south eastern Arabian Sea

 

Volume 58 Issue 2

G. Sree Renjima, V. N. Sanjeevan, B. R. Smitha, C. B. Lalithambika Devi and M. Sudhakar.

10.6024/jmbai.2016.58.2.1958A-11

Abstract

Along the Kerala-Mangalore coast the peak spawning season of Indian mackerel coincides with the transition period from Spring Inter-monsoon to Summer Monsoon. The species spawn in the offshore waters (50 to 200 m isobaths) mostly in the South Zone and to a less extent in the North Zone. Mackerel mostly avoid the Central Zone for spawning and as nursery ground. Newly hatched larvae are 1.585 mm in standard Length (SL). Larval growth rates are significantly higher (0.339 mm D-1) in the May-June spawning stock as compared to the July-August spawning stock (0.203 mm D-1). Growth is allometric and involves the yolk-sac stage (1.49 mm to 2.84 mm SL), pre-flexion (1.80 mm to 3.3 mm SL), flexion (2.85 mm to 4.85 mm SL), and post-flexion (4.60 to 11.3 mm SL) stages. Mackerel larvae have only restricted swimming and manoeuvring abilities as their body depth is relatively higher, but have much better feeding abilities owing to their large mouth-gape. In the early stages of ontogeny, the larvae feed predominantly on microzooplankton and switch over to a diet dominated by Calanoid Copepods as they grow further.  Main nursery grounds of mackerel larvae are located along the thermal fronts associated with cold-core eddies. Inter-annual variations in the abundance of mackerel larvae are influenced by the strength of winds that favour upwelling.

 

Keywords

Mackerel larvae, upwelling, spawning, advection, flexion, turbulence, growth rate, eddies, surface currents, dispersion

Date : 30-12-2016