Population dynamics of the white spotted rabbitfish (Siganus canaliculatus Park, 1797) in Makassar Strait and Gulf of Bone, Indonesia

Abstract

The white spotted rabbitfish (Siganus canaliculatus Park, 1797) is a locally important foodfish across much of Indonesia. This study aimed to support population dynamics-based fisheries management of white spotted rabbitfish stocks in the Makassar Strait and Gulf of Bone through providing data on age classes (cohorts), growth, mortality, and exploitation rate. Field data were collected over the year from February 2017 to January 2018. A total of 2248 white spotted rabbitfish (1810 males and 438 females) were collected from the Makassar Strait and 1686 (1277 males and 409 females) from the Gulf of Bone. The fish were measured (L = total length in mm), and all analyses were implemented in FISAT II. Cohorts were determined by sex based on monthly length-frequency data using the Bhattacharya method. The growth factor K and asymptotic length L∞ of white spotted rabbitfish in the Makassar Strait were K = 0.42/yr and L∞ = 211.98 mm with t0 = -0.250 yr for males and K = 0.43/yr, L∞ = 215.00 mm and t0 = -0.386 yr for females. In the Gulf of Bone the values were K = 0.42/yr, L∞ = 211.98 cm and t0 = -0.250 yr for males and K = 0.43/yr, L∞ = 215.00 mm and t0 = -0.386 yr for females. Mortality parameters of white spotted rabbitfish in the Makassar Strait were total mortality Z = 1.70/yr, natural mortality M = 0.76/yr, F = 0.94/yr giving an exploitation rate of E = 0.55 for males, while for females Z = 1.77/yr, M = 0.84/yr, F = 0.93/yr and E = 0.53. In the Gulf of Bone, for male white spotted rabbitfish Z = 1.78/yr, M = 0.60/yr, F = 1.18/yr and E = 0.67, while for females Z = 2.42/yr, M = 0.60/yr, F = 1.82/yr and E = 0.75/yr. These data indicate heavy fishing of both stocks, most likely at unsustainable levels.