Stock Assessment of Parrotfishes “Molmol” (Sub-Family Scarinae, Family Labridae) in the Major Fishing Grounds of Bohol, Central Visayas

Abstract

The issue on the overfishing of parrotfishes, locally known as “molmol” (subfamily Scarinae under family Labridae), in the coastal waters of Bohol province in Central Visayas has been raised by the Provincial Agricultural and Fishery Council (PAFC) of Bohol through Resolution No. 1 series of 2018 that pushes for the implementation of “open and closed fishing season” of all parrotfishes in the entire province. In any management intervention, baseline assessment of the stocks in question should be done as a significant basis for appropriate measures to be taken, thus this study. In Bohol, apart from the economic value, they carry essential functions in maintaining the ecological balance in the reef ecosystem. Parrotfishes are considered economically important as preferred fish among locals and tourists. The stock assessment of parrotfishes in Danajon Bank in the Bohol Sea and Cebu Strait was conducted by the National Stock Assessment Program (NSAP) Region 7 from 2015 to 2018 in 16 coastal municipalities of Bohol. It recorded 24 Scarine species across six genera. The green humphead parrotfish (Bolbometopon muricatum), categorized as vulnerable under the International Union for Conservation of Nature (IUCN) red list, was noted in Cebu Strait in 2015. Scarus ghobban, comprising 82.25%, dominated the catch in Danajon Bank; Scarus forsteni (30.07%) in Bohol Sea; and Chlorurus sordidus (58.45%) in Cebu Strait. Among the Scarines, S. ghobban dominated across fishing grounds from 2015 to 2018 with an aggregate of 10,267.69 kg (or 63.94%) monitored catch equivalent to 0.26% relative to all other species surveyed in the same period. The assessment also indicated that among the 22 fishing gear types being observed as used in catching parrotfishes, speargun is the most prevalent or frequently used. Moreover, the same assessment showed that the catch seasonality of S. ghobban determined from spear gun appears to be abundant during the first quarter in a year; in June, August, and December when higher monthly mean Catch per Unit Effort (CPUE) were also noted. However, the annual mean CPUE of speargun has decreased from 11.93 kg/day in 2017 to 9.22 kg/day in 2018. Population parameters of S. ghobban as the top one species were estimated using the FAO-ICLARM Stock Assessment Tools (FISAT) software and Froese Indicator Tool. Biological indicators for S. ghobban show signs of overfishing as reflected on its high fishing mortality (F/M), decreasing average length below maturity length, decreasing catch per unit effort in the current year, low percentage of mature in the catch, and increasing exploitation ratio (E). All of which already breached the limit reference points. In 2017 and 2018, the mature size composition of the catch was only 1.9 percent and 0.3 percent, respectively, far off from the 90-100% target and below the 50% limit. The values indicate that majority of the samples were small sizes; however, it cannot be determined if they were juveniles since this study excludes reproductive sampling. Optimum length (Lopt) was estimated at 29 cm (Total Length); lengths within ± 10% Lopt range at 26.1 to 31.9 cm and megaspawner at 31.9 cm up. Based on the results, suggested recommendations are indicated herein for possible consideration of the policymakers.