This study assessed the economic profitability of cultured local mudfish (Channa striata) fry reared in net cages under an extended photoperiod for a 28-day trial. The experiment applied two treatments: one with a natural photoperiod (natural) and the other with a 24 h photoperiod (24L:0D). Fry provided with a 24 h photoperiod grew faster than fry provided with a natural photoperiod. Fry grown under light-aided conditions reached the desired size for nursery culture (33.67±0.25 mm) within 2 weeks. Thus, the provision of a continuous photoperiod in larval culture shortened the hatchery phase. Notably, the abundance of zooplankton at night was significantly higher (p<0.05) in the light-aided condition (3091.09±1028.80 individuals L-1) compared to the control treatment with natural photoperiod (1240.92±675.70 individuals L-1). Increased prey availability contributed to the enhanced growth rate of the fry. Further, treatment with continuous photoperiod (24L:0D) has a significantly higher (p<0.05) survival rate (69.56±2.47%) compared to the treatment with a natural photoperiod (23.11±11.33%). Moreover, the economic analysis revealed that 24L:0D yielded a higher net profit (PHP 205,588.60) and a higher return on investment (56.02%) than the natural photoperiod treatment, indicating its feasibility as a cost-effective rearing strategy. No significant difference (p>0.05) was observed in the nutritional profile of fry reared under both treatments, indicating that extended photoperiod primarily influenced growth performance and survival rather than composition.
Erratum to: Phillip J Fish. DOI: 10.31398/tpjf/32.2.2024-0026 The authors would like to correct the error in the surname of one of the references for both in-text citations and the reference list. The incorrect spelling used was: “Supersales, J.B.” (Int J Ecosyst Ecol Sci. 4(3):433–442) The correct spelling should be: “Superales, J.B.”
Milkfish (Chanos chanos) is one of the most important finfish species in Philippine aquaculture. However, its processing and consumer acceptability are hindered by the presence of “spicule-like” intermuscular bones (IBs), a feature that has received limited research attention. In this study, milkfish samples of varying sizes, from larval to sub-adult stages, were examined to visualize IB development and describe their morphology. Differential bone staining and tissue clearing techniques revealed skeletal elements derived from either cartilage or tendon. Through this approach, IBs were identified and documented in detail with respect to their number, morphology, and ossification patterns, allowing classification into epineurals, epipleurals, and epicentrals. Among these, epineurals, particularly those at the anterior region of the body, exhibited the most complex morphology, while ossification was observed to proceed in a posterior-to-anterior sequence. To understand the mechanism of IB formation, a preliminary molecular analysis was carried out, which identified potential milkfish homologs of IB-associated genes runx2b and bmp6. These findings provide a useful baseline for future studies on the molecular basis of IB development and ossification in milkfish. Such work could pave the way for breeding strategies that aim to produce milkfish with reduced or absent IBs, ultimately improving processing efficiency, consumer safety, and market value.
KEY POINTS •Populations of all giant clam species in the Philippines have declined significantly over the past four decades, with a collective decline of 98%. • Despite massive culture and restocking efforts for the true giant clam (Tridacna gigas) since the 1980s, recruitment rates for the species are still very low, mainly because of persistent threats from anthropogenic activities, habitat degradation, and extreme weather events. • The harvest and trade of giant clams and their derivatives have been completely banned in the Philippines since the 1990s; however, live giant clams, meat, and shells are still sold illegally around the country up to the present. • Based on the best available information gathered, the assessment showed that the harvest and trade of giant clam shells pose a high risk to all species and are detrimental to the survival of wild giant clam populations in the Philippines. • The Scientific Authority is, therefore, unable to issue a positive non-detriment finding (NDF) for giant clam shells at this time, and trade must be confined to certified captive-bred specimens and their derivatives.
This study evaluates the heavy metal content in milkfish (Chanos chanos) sold in Metro Manila to assess its safety for human consumption. Milkfish samples were collected from public markets across the National Capital Region (NCR) and analyzed for lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As) using Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES). The analysis revealed lower concentrations of these metals than in previous studies, with Pb at 0.07 ppm, Cd at 0.03 ppm, Hg at 0.04 ppm, and As at 0.01 ppm—all within the permissible limits set by both the Bureau of Fisheries and Aquatic Resources (BFAR) and the European Union. These results suggest a positive effect of better aquaculture practices and environmental monitoring in milkfish farms in the NCR region. While the findings confirm the safety of Metro Manila milkfish, continued monitoring and the expansion of studies to other regions are recommended to ensure nationwide food safety.
