The use of natural immunostimulants as alternatives to antibiotics has gained attention in aquaculture to mitigate disease impacts. In this study, we evaluated fucoidan extracted from giant bull kelp (Durvillaea potatorum) as a dietary additive in black tiger shrimp (Penaeus monodon). Four experimental diets containing increasing levels of fucoidan (0, 1.0, 2.5, and 5.0 g kg⁻¹ diet) were tested for their effects on growth, non-specific immune parameters, and survival against white spot syndrome virus (WSSV) and acute hepatopancreatic necrosis disease (AHPND)-causing Vibrio parahaemolyticus. After 30 days of feeding, fucoidan supplementation did not adversely affect shrimp growth or culture survival, even at the highest inclusion level (5 g kg⁻¹). Non-specific immunological indices, including total hemocyte count (THC), differential hemocyte count (DHC), phenoloxidase (PO) activity, plasma total protein (PTP), and plasma agglutination titer (PAT), were enhanced by fucoidan supplementation, with improvements observed even at 1 g kg⁻¹ relative to the control group. Activation of non-specific immunity translated into increased resistance against WSSV and AHPND, with the highest survival recorded in shrimp fed 5 g kg⁻¹ fucoidan, followed by 2.5 g kg⁻¹. In comparison, similar survival rates against WSSV and AHPND were observed in the unsupplemented control and 1 g kg⁻¹ fucoidan. Overall, this study demonstrates that dietary inclusion of D. potatorum fucoidan at 5 g kg⁻¹ effectively enhances immune responses and disease resistance in P. monodon without negatively impacting growth performance, highlighting its potential as a functional feed additive in shrimp aquaculture.

Hypnea is a cosmopolitan genus of red seaweeds and an important source of carrageenan worldwide. However, Hypnea species remain largely unutilized in seaweed aquaculture in the Philippines. This study aimed to evaluate the growth performance and carrageenan properties of an indigenous, unexploited Hypnea sp. collected from Panay Island and to compare them with those of the commercially cultivated Kappaphycus striatus. In a field cultivation experiment, Hypnea sp. showed significantly higher biomass (145.1 ± 53.7 g) than K. striatus (92.9 ± 10.3 g) up to day 28 (p < 0.001), while no significant difference was observed at days 36 and 43. The final yields were 181.0 ± 68.4 g for Hypnea sp. and 191.1 ± 33.0 g for K. striatus (p > 0.05). Semi-refined carrageenan extracted from the cultured Hypnea sp. exhibited gel-forming capacity, suggesting the presence of κ-carrageenan. However, both the viscosity and gel strength of Hypnea sp. (9.52 ± 3.53 cP; 148 ± 41.6 g cm⁻²) were significantly lower in K. striatus (70.9 ± 49.4 cP; 456 ± 201 g cm⁻²) (p < 0.001), indicating that Hypnea sp. possesses distinct carrageenan properties from conventional commercial seaweed. Although further development of carrageenan-based products tailored to its unique properties will be required for commercial utilization, these findings highlight the potential of Hypnea sp. as a candidate seaweed for aquaculture in the Philippines.

Vibriosis, a bacterial disease, is considered a significant threat to the sustainability and economic viability of shrimp production. The present study evaluated the application of a predatory bacterium to control the population growth of pathogenic Vibrios in Pacific whiteleg shrimp (Penaeus vannamei). The predatory bacterium was identified as Bacteriovorax sp. OP175948.1 based on the 16S rRNA sequence. The Vibrio-inhibitory activity of Bacteriovorax sp. was evaluated using two independent trials with P. vannamei, exposed to two pathogenic Vibrios, including Vibrio parahaemolyticus and Vibrio harveyi. Each trial was conducted in five treatments, including a negative control, a positive control, and a treatment with Bacteriovorax sp. applied at 10², 10⁴, and 10⁶ plaque-forming units mL⁻¹ (PFU mL⁻¹). Results indicated that shrimp infected with V. parahaemolyticus and V. harveyi, and then treated with Bacteriovorax, showed a 6-fold increase in survival for V. parahaemolyticus and a 3-fold increase for V. harveyi, relative to the control. The shrimp treated with 10⁴ to 10⁶ Bacteriovorax sp. improved survival associated with a significant decline in Vibrio spp. counts in the shrimp tissues and rearing water. The Bacteriovorax sp. should be used as a practical strategy to prevent Vibrio-associated mortalities in P. vannamei aquaculture.

The excessive growth of seaweeds (macroalgal biofouling) on submerged cage structures is a severe operational constraint for fish cage aquaculture in tropical environments. This study investigated the species composition of macroalgal biofouling growing on the submerged structures of the fish cage aquaculture in Bongao Channel, Tawi-Tawi, Philippines, via a qualitative survey (e.g., snorkeling around the cage systems). The primary objective was to provide a taxonomic inventory of the colonizing seaweed species to understand the biological makeup of the fouling community. Through morphological examination of the collected samples, a total of 26 species belonging to 16 distinct genera were identified, representing the three major algal divisions: Chlorophyta (green algae) exhibited the highest generic richness, including Boergesenia, Caulerpa, Chaetomorpha, Cladophora, Halimeda, Boodlea, and Ulva. Rhodophyta (red algae) were represented by Acanthophora, Actinotrichia, Chondrophycus, Yonagunia, Gracilaria, Hypnea, and Endosiphonia, while Ochrophyta (brown algae) included Padina and Sargassum. The presence of various taxa, particularly filamentous Chaetomorpha and stoloniferous Caulerpa, identifies these groups as the key structural components of the biofouling community on the cage nets. Additionally, the inventory recorded the occurrence of economically valuable red algae (e.g., Gracilaria and Hypnea) and ecologically significant brown algae (e.g., Sargassum) within the assemblage. These findings establish a critical taxonomic baseline, providing the essential species-level data required to develop targeted mitigation strategies and sustainable management practices for the floating cage aquaculture in Tawi-Tawi.

Since 2000, SEAFDEC FishWorld has served as a focal point for community engagement in marine biodiversity conservation, with a particular emphasis on sea turtle protection in the waters surrounding Panay and Guimaras Islands. This book presents the outcomes of a long-term initiative involving the documentation, tagging, release, and care of sea turtles incidentally captured in local fisheries. It provides a permanent record of 335 sea turtles, including documentary photographs of 214 individuals, and offers extensive data and new insights into the status and ecology of these endangered species in Philippine waters. The volume details the interactions between sea turtles, fishing gear, and coastal communities, highlighting collaborative efforts among FishWorld, fishers, and government agencies to promote conservation and reduce turtle capture. Written for fishers, conservation practitioners, government officers, educators, and the general public, the book combines scientific information with accessible, pictorial presentation. It contributes significantly to national efforts to raise awareness, foster community participation, and strengthen the protection of sea turtles and the marine ecosystems that sustain them.

In aquaculture-based stock enhancement, releasing juveniles at larger sizes can increase their chances of survival. Moreover, on-site (or within the release area) nursery rearing or intermediate culture of hatchery-bred stocks is important for acclimatization prior to release. In the Philippines, the prospect for tiger shrimp (Penaeus monodon Fabricius 1798) intermediate culture was evaluated in the New Washington Estuary (NWE), Aklan, Philippines. Locally sourced postlarval (PL₁₃) tiger shrimp P. monodon were reared in a temporary netted pen within a disused pond with mangroves. Serendipitously, storm events occurred during a couple of our rearing trials (Runs 1 and 2). This provided us with the unique opportunity to assess the effects of rainstorms on the cultured PL using morphological and environmental data, measured before, during, and after storm events. Notably for Run 1, four distinct phases were identified: Acclimatization phase (ACCL), Stable phase (STBL), Storm phase (STRM), and Recovery phase (RCVR). Culture performance indicators like growth, survival/mortality rate, and condition factor (CF) revealed significant differences among phases. Mortality rate of − 6.4% d⁻¹, growth rate of 9.9% d⁻¹, and low CF (0.24) of shrimp in the initial first week (D1–D9 of ACCL before the storm) were associated with stress and density stabilization (from 325 m⁻² to 178 m⁻²). During STBL (D10–D18), stock conditions improved (growth: 20% d⁻¹, mortality: − 0.17% d⁻¹, CF: 0.49). However, this abruptly degraded during STRM (D20–D28) with negative growth rate (− 9.7% d⁻¹), high mortality (− 4.3% d⁻¹), and low CF (0.28), indicating very high stress levels of stocks induced by acute heavy rainstorms, leading to steeply fluctuated water temperatures. Subsequently, recuperation of stocks after the storm (D30 onwards) was significant during RCVR (Growth: 19% d⁻¹; Mortality: − 0.34% d⁻¹; CF: 0.41). Remarkably, the surviving shrimp (now > 0.5 g) became adapted and resilient, showing stable growth and survival despite another abrupt rainstorm with fluctuating water conditions at D45–46. On the other hand, Run 2 with a lower initial stocking density (56 m⁻²) showed better performance during ACCL (D1–10) and STBL (D11–30) with respective low mortality rates (− .2% d⁻¹ and − 0.75% d⁻¹) and high growth rates (24.4% d⁻¹ and 14.6% d⁻¹). However, two subsequent storms caused prolonged (> 10 d) rainfall during STRM, leaving only 4% survival at D38 with no RCVR phase. We showed that acute (~ 2 d) intense rainstorms can be detrimental to young (< 0.2 g) PL, but the stable environmental conditions after storms can allow the surviving stocks to recuperate, grow fast (> 0.5 g), then become quite resilient even to a subsequent acute (2 d) rainfall. However, extended rainstorms (> 10 d) cause continuous decline in salinity and temperature, leading to high mortality of shrimp. Therefore, careful programming of future on-site intermediate culture activities is important, considering the space and duration required for culture, initial densities and target sizes of PL, and cautious account of rainstorm seasonality.

Sea cucumbers are ecologically and economically important marine invertebrates, whose wild populations have been threatened by overfishing in recent decades. The rapid decline in wild stocks was driven by high market prices of sea cucumber products for food and medicine. Fortunately, recent developments in hatchery seed production technologies have paved the way towards establishing a more sustainable sea cucumber industry through aquaculture without dependence on massive collections from natural populations.

While rotifers are important first live feed in marine fish hatcheries, maintaining the rotifer culture collection by feeding live microalgae and water exchange is laborious and costly. It is therefore necessary to streamline the culture collection protocol and reduce operating costs. The use of microalgal paste in rotifer production is well documented, but there is limited information on its use in rotifer culture collection because of its ability to deteriorate water quality, such as increasing unionized ammonia (NH₃). This study aimed to determine the effectiveness of bioflocs (BF) in regulating NH₃ in rotifer culture collection fed microalgal paste Fresh Chlorella V12 (CV12) under zero-water exchange (ZWE) conditions for 42 days. The marine rotifers Brachionus plicatilis were subjected to six treatments, namely: (1) Nannochloropsis oculata (Nanno) × weekly water exchange (WWE), Nanno × WWE as the control, (2) CV12 × WWE, (3) Nanno × ZWE, (4) CV12 × ZWE, (5) Nanno + BF × ZWE, and (6) CV12 + BF × ZWE. Rotifer density was estimated every 3 days, while NH₃ was measured weekly. Bacterial compositions were determined. On day 42, the lowest NH₃ was observed in CV12 + BF × ZWE, which was significantly different from CV12 × WWE and CV12 × ZWE. Rotifer density was higher in Nanno + BF × ZWE and CV12 + BF × ZWE than in CV12 × ZWE, but egg-bearing rotifers were similar in all treatments on day 42. Single initial inoculation of BF maintains water quality by regulating NH₃ concentration via the activity of ammonia oxidizer Nitrosomonas nitrosa and the bacterial groups under phylum Chloroflexota in the long-term B. plicatilis culture collection and that microalgal paste combined with BF can be a cost-effective alternative to live microalgae.