Polychaetes are of high commercial interest as potential feed in aquaculture industry. Despite this, knowledge of polychaete culture is limited. The goal of this study is to develop a protocol that maximizes survival and growth of polychaetes from embryonic to juvenile stages. To determine the effect of light intensity and photoperiod on Marphysa iloiloensis, two experiments were conducted; 1 - hatchability (embryo-larva; 24 h duration) and 2 - survival and growth (larva-juvenile; 29 d duration). Both experiments followed a 3 × 3 factorial design using three light intensities (3.4, 64.4, and 157 μmol m⁻² s⁻¹) and three photoperiods (1 L: 23D, 3 L: 21D, and 6 L: 18D) with four replicates each. The best light regime was compared to the control (0 μmol m⁻² s⁻¹). Hatching success was significantly lower in treatments exposed to 157 μmol m⁻² s⁻¹ regardless of photoperiod (P < 0.05). Survival at juvenile stage was significantly dependent on the interaction between light intensity and photoperiod (P < 0.01). Survival was higher in both 0 μmol m⁻² s⁻¹ and 3.4 μmol m⁻² s⁻¹ (all photoperiods). Survival decreased significantly in 64.4 μmol m⁻² s⁻¹ and 157 μmol m⁻² s⁻¹ under both 3 L: 21D and 6 L: 18D photoperiods. Prolonged exposure to higher light intensity compromised the survival of the polychaete from larval to juvenile stage while growth was not affected. These findings suggest that either continuous darkness or a light intensity of 3.4 μmol m⁻² s⁻¹ is the best culture condition from embryonic to juvenile stage of mud polychaete M. iloiloensis to optimize production.

Aeromonas load and species composition in the rearing water, sediment, gills and intestines of healthy tilapia Oreochromis niloticus collected every 2 weeks from Days 30 to 120 after stocking in six earthen ponds in the Philippines were determined. Presumptive Aeromonas counts (PACs) in the water and sediment ranged from 10¹–10³ c.f.u./ml and 10¹–10³ c.f.u./g while in the gills and intestines, PACs ranged from 10⁴–10⁷ c.f.u./g and 10²–10⁵ c.f.u./g, respectively. Presumptive Aeromonas counts in the water, sediment, and gills of tilapia varied among days of culture while in the intestines of tilapia, PACs markedly dropped by approximately 2 logs at Day 75 and either remained in the same level or decreased by another 1 log at Day 120 of grow‐out culture. Aeromonas hydrophila predominantly constituted 94% of all presumptive Aeromonas spp. examined (n = 343), followed by A. sobria (4%) and A. salmonicida (2%). Taken together, current data provide some putative threshold levels of tilapia reared in earthen ponds to Aeromonas spp. The dominance of A. hydrophila together with negligible population of A. salmonicida and A. sobria indicate that Aeromonas are common commensal bacteria in tilapia and their environment which under conditions of stress could instigate disease epizootics.

We developed a specific competitive enzyme-linked immunosorbent assay (ELISA) for yellowtail kingfish (Seriola lalandi) follicle stimulating hormone (FSH). We previously produced a full-length single chain recombinant yellowtail kingfish FSH using the Pichia pastoris expression system. We used the same method to produce the β subunit of the hormone, against which polyclonal antibodies were raised in rabbits. We first confirmed immunoreactivity of the polyclonal antibodies with the recombinant full length FSH and FSHβ as well as plasma and pituitary FSH of sexually immature and mature yellowtail kingfish by Western blot analysis. We then developed a precise and reproducible ELISA for yellowtail kingfish FSH and validated the assay in plasma and pituitary extracts. The intra- and inter-assay coefficients of variation was <2.2% and 10.2%, respectively. The sensitivity of the assay was 78 pg/ml. For further validation of the assay, we measured the plasma FSH in immature yellowtail kingfish treated with increasing doses (blank, 50, 100 and 150 µg/kg) of kisseptin2-10 peptide from a previous study. The dose response observed in treated females was not significant, however the increased plasma FSH levels coincided with the significantly higher estradiol levels we previously reported in the treated groups. We assessed the applicability of the assay in measuring circulating FSH in other species. We observed parallelism between the linearized FSH standard curve and displacement curves of serially diluted plasma from Atlantic bluefin tuna (Thunnus thynnus) and tilapia (Oreochromis niloticus). We also observed similar parallelism with full length recombinant giant grouper (Epinephelus lanceolatus) FSH. The ELISA we developed for yellowtail kingfish FSH will be useful in understanding the reproductive biology of the species as well as enhancing its aquaculture.

A recombinant giant grouper Luteinizing Hormone (LH) consisting of tethered beta and alpha subunits was produced in a yeast expression system. The giant grouper LH β-subunit was also produced and administered to rabbits for antibody development. The recombinant LH and its antibody were used to develop an Enzyme Linked Immunosorbent Assay (ELISA). This ELISA enabled detection of plasma LH levels in groupers at a sensitivity between 391 pg/ml and 200 ng/ml. Different species of grouper were assayed with this ELISA in conjunction with gonadal histology and body condition data to identify links between circulating LH levels and sexual development. We found that circulating levels of LH decreased when oocytes began to degenerate, and sex-transition gonadal characteristics were apparent when LH levels decreased further. When circulating LH levels were related to body condition (body weight/ body length), transitioning-stage fish had relatively high body condition but low plasma LH levels. This observation was similar across multiple grouper species and indicates that plasma LH levels combined with body condition may be a marker for early male identification in the protogynous hermaphrodite groupers.

This study was conducted to evaluate 8 commercial probiotic products being marketed for the grow-out culture of the tiger shrimp Penaeus monodon and the “SEAFDEC Indigenous Probiotic”. Bacterial parameters investigated consisted of: 1) inherent bacterial population, 2) Total Bacterial Count (TBC), 3) effect on Vibrio harveyi, and 4) presumptive Vibrio populations. Results showed that upon activation, the TBCs of Probiotics A, B, C, F, G and H were precisely as claimed in its product brochure at equal or +/- 1 log difference. In contrast, Probiotics D and E yielded TBCs that were 3 and 2 logs lower than stated in their respective product brochures. At 24 h after pond water inoculation, Probiotics A and E caused an almost 2 logs increased TBCs, Probiotic F a one log increase while no apparent differences from the control were observed in the TBCs of the other test probiotics. The “SEAFDEC Indigenous Probiotic”, Probiotics A, G and H induced the inhibition of luminescent Vibrio by 100% for 48 h exposure, 90% in 24 h, 84-63% in 5-6 days and 77-81% in 5-6 days, respectively. However, such inhibitory effect was not sustained on extended periods. In contrast, the other test Probiotics did not inhibit luminescent Vibrio. On the contrary, Probiotics C, E and F even resulted in a 2 and 1 log increase of the V. harveyi population. For the presumptive Vibrio counts, Probiotics B, E and F had 1-2 logs higher numbers of green colonies than controls while Probiotics A and E yielded higher numbers of yellow colonies. This study showed that inoculation of the shrimp pond waters with Probiotics A, C, D, E and F caused at least one log increase in TBCs. The TBCs of the Probiotics in the presence of ammonia, nitrite and phosphate were affected by the presence or absence of aeration.

Sea-based culture of early juvenile sandfish Holothuria scabra up to fingerling size (>2 g) using floating hapa nets has been confirmed as a viable nursery system in tropical countries such as the Philippines. However, production can be further optimized through more efficient rearing practices. In this study, we demonstrate the effects of initial stocking density, size grading and net replacement frequency during the culture of early juvenile sandfish in sea-based floating hapa nets (2 × 1 × 1 m). Testing different initial stocking density treatments ranging from 150 to 2000 early juveniles (4–10 mm; 0.02–0.06 g) per hapa net, we confirmed significantly faster growth (0.06–0.08 g d⁻¹) and higher survival (72–97%) in low densities (≤500 hapa⁻¹), compared to high densities (≥700 hapa⁻¹: 0.02–0.04 g d⁻¹; 67–80%). Low density culture can produce 2 g sandfish in about a month, while higher densities will require a 2–3 mo culture period to reach this size. Culture performance following size grading was also compared using three initial size classes (small, 0.05–0.99 g; medium, 1–1.99 g; and large, 2–3 g) and a mixed group (0.05–3.00 g). At 45 d, juveniles in pooled size-graded groups grew significantly faster (0.11–0.13 g d⁻¹) than those in the mixed group (0.01 g d⁻¹). Survival was significantly higher in the medium (85.3%) and large (84.7%) groups, than those in the small (54.4%) and mixed (45.6%) groups. However, size variation was not significantly mitigated by grading during the 45-d culture. Culture performance of sandfish was not significantly enhanced by more frequent net replacement for short-term rearing (30–45 d). Optimal results were gained from an initial stocking density of ≤500 early juveniles (5–10 mm) per floating hapa net which may be cultured in a month, without requiring net replacement and size grading to produce ≥2 g sandfish. However, in cases of high hatchery production, it is also feasible to adopt higher density stocking (e.g. >1000 hapa⁻¹), but will require longer culture duration (60–85 d), monthly net replacement and size-grading to attain the same size. Results of this study can help fine-tune management practices for nursery culture of sandfish in sea-based floating hapa net nurseries in order to boost production of fingerlings needed for aquaculture and restocking.

The efficient level of MBM for good growth and survival of milkfish, Chanos chanos Forsskal, without histological changes in tissues (liver, intestine, muscle, kidney and brain) was determined in both freshwater (FW) and seawater (SW) culture conditions. To determine this level, growth and digestibility experiments were conducted in FW and SW together with observations on histology of tissues. In the growth experiments, fish (wet weight less <5g) in triplicate groups were fed for three months with either of the six test diets formulated to be isonitrogenous at 36% with varying dietary levels of MBM at 0%, 7.5%, 15%, 22.5%, 30% and 37.5%. The apparent digestibility coefficients of crude protein and crude fat in diets were determined using a dietary indicator (Chromic Oxide). Intestinal content of fed fish (wet weight, 85g – 65g) were collected by stripping the last posterior third of the intestine. Milkfish survival was 100% in all treatments in FW. Protein of MBM was more digestible to milkfish in SW (93.64%) than in FW (67.34%). Based on growth efficiencies, survival data, and histology of tissues examined, milkfish was able to utilize dietary level of MBM at 30% in FW and at 22.5% in SW. Assimilation of organic matter in test diets that contained MBM at 7.5% to 30% were high (88% - 93%) in both FW and SW.

Donkey's ear abalone (Haliotis asinina) is a gourmet seafood export of the Philippines but its wild stock is at risk due to high fishing pressure. This paper aims to show evidences that abalone seeds produced in hatcheries can be used to rehabilitate its fisheries in multi-use buffer zones of marine reserves. This study released hatchery-reared abalone juveniles in a community-based resource enhancement site located in multi-use reef surrounding Molocaboc. This island is populated by fisherfolks who participated in protecting the 4000 m2 coralline release site. Molocaboc Reef comprise the buffer zone of Sagay Marine Reserve in Negros Occidental province in central Philippines. Data obtained during monthly monitoring of the release site from 2011 to 2016 showed that hatchery-reared abalone established together with its wild counterparts. Baseline wild abalone catch per unit effort (CPUE = 3 divers 1 h fishing) is 0.005/100 m2 in 2011. Mean monthly CPUE after release increased to 53 hatchery-reared and wild individuals combined. The mean shell length, body weight and body mass index of the hatchery-reared individuals (6.4 cm, 70.9 g, 10.5 g/cm) is not significantly different from those of the recovered wild stocks (6.9 cm, 85.0 g, 12.0 g/cm). The stocks recovered in the midst of undisrupted fishing activities in areas immediately outside and beyond the release site. Thus, mass production of seeds of overfished species is advised to repopulate degraded fisheries, improve catch of fisherfolks living within buffer areas of marine reserves and contribute to production and trade of high-value species.

Crabs and shrimps (order Decapoda) use colours in various tasks such as foraging and mate choice. Colour vision requires at least two types of photoreceptors with different spectral sensitivities. Previous physiological studies revealed that most crabs including Scylla mud crabs have a single visual receptor system, i.e. they are colour blind. We determined colour vision by means of a behavioural experiment on hatchery-produced and wild-captured purple mud crab Scylla tranquebarica in a roofed hatchery. Adult crabs (8-10 cm carapace width) were subjected to classical conditioning to associate a food reward with a blue or a green stimulus placed among seven shades of grey. The hatchery-produced crabs learnt this task after 14 days of reward training, and thereafter distinguished blue in 27 non-reward trials, and green in 39 non-reward trials. The wild-captured crabs did so after 25 days of reward training, and distinguished green in 49 non-reward trials. These results indicated colour vision in S. tranquebarica. However, the crabs were unable to distinguish blue or green in dim light of 4.4 cd/m² (which is slightly brighter than full moon light). The high colour vision threshold was attributed to the small optic parameters of the apposition compound eyes of S. tranquebarica.

Each year a significant proportion of global food production is lost to pests and diseases, with concerted efforts by government and industry focussed on application of effective biosecurity policies which attempt to minimise their emergence and spread. In aquaculture the volume of seaweeds produced is second only to farmed fish and red algal carrageenophytes currently represent approximately 42% of global production of all seaweeds. Despite this importance, expansion of the seaweed sector is increasingly limited by the high prevalence of recalcitrant diseases and epiphytic pests with potential to emerge and with the demonstrated propensity to spread, particularly in the absence of effective national and international biosecurity policies. Developing biosecurity policy and legislation to manage biosecurity risk in seaweed aquaculture is urgently required to limit these impacts. To understand current international biosecurity frameworks and their efficacy, existing legislative frameworks were analysed quantitatively for the content of biosecurity measures, applicability to the seaweed industry, and inclusion of risks posed by diseases, pests and non-native species. Deficiencies in existing frameworks included the following: inconsistent terminology for inclusion of cultivated seaweeds, unclear designation of implementation responsibility, insufficient evidence-based information and limited alignment of biosecurity hazards and risks. Given the global importance of the cultivation of various seaweeds in alleviating poverty in low and middle income countries, it is crucial that the relatively low-unit value of the industry (i.e. as compared with other aquatic animal sectors) should not conflate with a perceived low risk of disease or pest transfer, nor the subsequent economic and environmental impact that disease transfer may impact on receiving nations (well beyond their seaweed operations). Developing a clear basis for development of robust international biosecurity policies related to the trade in seaweeds arising from the global aquaculture industry, by first addressing the gaps highlighted in this study, will be crucial in limiting impacts of pests and diseases on this valuable industry and on natural capital in locations where seaweeds are farmed.