Increasing gill raker numbers in juvenile and young skipjack tuna (Katsuwonus pelamis)

Abstract

An increase in gill raker numbers in skipjack tuna (Katsuwonus pelamis) was observed during the development of juvenile and young stages (26–187 mm in standard length (SL)). Examination of 104 individuals showed obvious increments in number with growth, until 80–100 mm SL. Subsequently, numbers increased slowly (to 59 in the largest specimen), indicating that gill raker development in skipjack tuna is slower than in other scombrid fishes, such as Thunnus. However, gill raker numbers in juvenile and young skipjack tuna stages remain a useful taxonomic character.