Grow-out culture of the abalone Haliotis asinina in Guimaras, Philippines: Comparison of tubes and drums as culture containers and the effects of serpulid infestation

This study compared tubes and drums as containers for the grow-out culture of abalone Haliotis asinina using mixed seaweeds and formulated diet as feed. The recycled drums were newly tested containers for abalone culture as the cheaper and larger alternative. However, on the 10th month of culture, serpulids (Pomatoceros sp. and Spirorbis sp.) were observed on the abalone shells; hence, the 12-month culture was extended to 16 months to observe further the effects of these ectoparasites on the growth and survival of abalone. Throughout the culture period, abalone reared in tubes had significantly higher mean shell length and body weight than those reared in drums, measuring 45.42 ± 0.36 mm, 23.40 ± 0.99 g, and 41.45 ± 0.23 mm, 18.26 ± 0.40 g at harvest, respectively. Mean growth rates of those in tubes were significantly higher than those in drums before serpulid infestation but did not differ during months of infestation. Survival was consistently higher in tubes than drums, except during May–September 2023. At harvest, survival in tubes was 46.7 ± 11.0%, 37.8 ± 5.9% in drums. Daily water temperature ranged 28.00–32.33 °C, salinity 16.00–34.37 ppt. Monthly readings (ppm) of dissolved oxygen ranged 3.1–7.4, sulfide 0.00–0.73, phosphate 0.01–0.87, nitrate 0.00–0.99, nitrite 0.00–0.22, and total suspended solids 0.22–4.83. In April–October 2023, serpulids became prevalent (tubes = 31.5 ± 3.4%; drums = 38.3 ± 3.4%) when mean DO was significantly lower and sulfide higher than in June 2022-March 2023. These fluctuations in water parameters may have triggered the infestation, resulting in lower growth rates and abalone survival. But, despite these fluctuations and infestations, tubes remained a better culture container for the abalone.The project was funded by the Southeast Asian Fisheries Development Center Aquaculture Department (Budget Code 5311-T-TV-M0222T; Study Code TV-02-M0222T)

Giant freshwater prawn culture

This brochure provides information on the culture of the giant freshwater prawn (Macrobrachium rosenbergii), detailing hatchery, nursery, and grow-out operations. Key highlights include larval rearing, nursery, and grow-out techniques developed by SEAFDEC/AQD. The brochure also presents the economic feasibility of giant freshwater prawn farming both in ponds and in cages

AQD Matters 2025 January - February

In this issue: 1) Bangsamoro eyes lapu-lapu farming with SEAFDEC expertise; 2) Equipment delivered for BFAR-SEAFDEC Feed Mill in Tigbauan; 3) Aquaculture training draws 296 trainees in 2024; 4) SEAFDEC/AQD employees attend "Pag-IBIGfluencer" seminar; 5) Temasek University sends experts to SEAFDEC/AQD for training; 6) SEAFDEC/AQD conducts training on oyster seed production; 7) 7 complete training course on tilapia hatchery and grow-out operations; 8) More seaweed samples collected to boost research; 9) DFA officials visit SEAFDEC/AQD stations; 10) Memorandum inked for SEAFDEC-LGU collaboration for sea cucumber project; 11) Pest to Feed: Snail as supplemental diet for pompano

Development of aquaculture techniques on new aquatic species to create and promote a local aquaculture industry in Southeast Asia

Aquaculture achieved a significant milestone in 2022, surpassing capture fisheries production as the leading aquatic producer. Its global production reached 130.9 million t, with 94.4 million t comprising aquatic animals, marking a 4.4 % surge from 2020 (FAO, 2024). This milestone, coupled with the decline of capture fishery production due to overexploitation and overfishing, underscores the need to explore and develop aquaculture techniques for new aquatic species. Once established, these techniques will be promoted and hopefully create a new local aquaculture industry in Southeast Asia. Recognizing the unparalleled success and expertise of the Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC/AQD) in the development of aquaculture technologies, especially in the broodstock management, spawning, larval rearing, nursery and grow-out culture, fish nutrition, and fish health management, this study, with funding support from the Japanese Trust Fund (JTF), aims to develop aquaculture techniques for new aquatic species, namely: slipper lobster (Thenus orientalis), kawakawa (Euthynnus affinis), and shortfin scad (Decapterus macrosoma). Furthermore, this study was conducted to generate basic information on reproductive biology, breeding, farming techniques, feeding habits, fish health, and other relevant data for developing aquaculture techniques of the three species through the collection from identified sites, transport, stocking, and management of broodstock, larval rearing, feeding, and health management experiments

The complete mitochondrial genome of freshwater gammarid Gammarus nipponensis (Crustacea: Amphipoda: Gammaridae)

This study presents the complete mitochondrial genome sequence of Gammarus nipponensis, a freshwater crustacean found in the western regions of Honshu, Shikoku and Kyushu in Japan. The entire genome is 16,429 bp in length, encoding a standard set of 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes, as well as the putative control regions. The mitochondrial genome of G. nipponensis is characterized by a high concentration of A and T nucleotides (67.1%). Notably, the mitogenome contains long TATTTTA repeats in the control region 2 at 686 bp long. This newly available genome information will be useful for studying the evolutionary relationships within the genus Gammarus and for understanding diversification among G. nipponensis populations

Seasonal growth, carrageenan properties, and resistance to disease and epiphytic pests between Kappaphycus alvarezii (Rhodophyta) var. tambalang (brown) tissue-cultured and farm-sourced seaweeds

Growth performance (specific growth rate [SGR] and biomass yield), carrageenan properties (yield, viscosity, and gel strength), and disease and pest incidence were compared between Kappaphycus alvarezii var. tambalang (brown) tissue-cultured (TC) plantlets and farm-sourced (FS) seedlings. Seedlings used in the trials were propagules (4‒19 g pieces) and these were deployed on lines in sea cages over three separate runs of 60 days. The highest growth rate was recorded in TC plantlets and the SGRs were significantly higher (1.5‒6.5x) in TC than FS after Day of Culture (DOC) 15 (i.e., measurements taken every 15 days in each cycle). The carrageenan properties did not differ between treatments, with the exception of viscosity at DOC 45, where TC was higher than FS. “Ice-ice” disease (IID) was observed in both FS and TC in May‒June and August‒October at DOC 45 to 60, coinciding with changes in environmental conditions (i.e., dry‒wet and wet seasons). IID in FS had a moderate to very high incidence (31.2‒86.2%), while TC IID had a lower range of incidence (12.8‒60.6%). On the other hand, epiphytic filamentous algae (EFA) were observed only in August‒October with a low incidence (≤25%). However, EFA appeared earlier in FS than in TC. Taken together, these results highlight that tissue-cultured seaweeds had higher growth performance without compromising carrageenan quality and may be more resistant to health problems than farm-sourced seedlings. Studies should now assess the long-term viability of using tissue-cultured seaweeds over farm-sourced seedlings scaling to allow testing in standard farm settings, including the size of the initial seed.The study is supported by SEAFDEC/AQD with study code DP-01-S2020I

Ecology, distribution, and recruitment of conch (Gastropoda: Strombidae) in intertidal zones

Macroinvertebrates from Family Strombidae locally known as "sikad-sikad" are some of the major gleaned species in the intertidal areas. This study investigated the ecology, abundance, distribution, and recruitment of conch species of Family Strombidae in the three coastal barangays (Pandaraonan, Dolores, and Tando) of Guimaras Island. The ecological aspects were assessed for three habitat types (seagrass beds, bare sand, and edges of mangrove areas) within each barangay. A total of 319 conch individuals were identified belonging to seven species (Canarium erythrinum, Canarium labiatum, Canarium mutabile, Canarium urceus, Conomurex luhuanus, Gibberelus gibbosus, and Laevistrombus canarium). The distribution of these species varied across habitats but were found most abundant in Enhalus acoroides and Thalassia hemprichii seagrass beds with patchy distribution exhibited by regular or clumping patterns. Shell lengths ranged from 15–50 mm with C. mutabile being the smallest and C. luhuanus and L. canarium as the largest species. Temporal assessment at one site (i.e., seagrass beds of Dolores) showed no significant variation in the abundance and size of adult conch species across monitoring months. However, conch juveniles assessed showed increasing trend in shell length (5, 8, and 12 mm) but with decreasing density (103, 104, and 90 individuals/m2) from February to April, and June 2023, respectively. This study provides relevant information in the development of policies to ensure sustainability of conch as a valuable fisheries commodity

Bioremediation of oil spills: Current status, challenges, and future prospects

The petrochemicals produced from refining oil have become a large part of human life, making oil a valuable and expensive commodity. As a non-renewable resource, extraction and transport efforts have intensified to keep up with the demand, increasing the occurrences of oil spills. Such accidents have devastating impacts on the environment, the health of organisms, and a country's economy like the Philippines, and thus, need to be resolved immediately. One way to deal with oil spills is through bioremediation but the process is still facing several challenges. For one, the toolbox for bioremediation is limited. About 79 genera of bacteria were observed to degrade oil but there are only a small number of bacterial species and/or strains that have been recognized as useful for bioremediation. Second is that most oil-degrading bacteria found have low oil degradation efficiencies. Another challenge is keeping the bacteria alive to carry out the process. Fortunately, progress has been made in solving these challenges. Researchers are now testing different consortia, including bacteria–bacteria, bacteria–fungi, bacteria–microalgae, that can complement each other such as biosurfactant-producing bacteria with different oil-degrading microorganisms or microalgae or fungi that enhance the growth of oil-degrading bacteria. A consortium like this improves the survivability of each microorganism and enhances the oil-degrading efficiency. Moreover, the search for additional oil-degrading and biosurfactant-producing bacteria and other microorganisms to add to the bioremediation toolbox has been improved with the emergence of high-throughput sequencing. Aside from microorganisms, seaweeds have shown potential for bioremediation. The seaweed Caulerpa prolifera has been demonstrated to degrade diesel up to a certain concentration with the help of the bacteria growing on its surface. Bioremediation has a long way to go, but recent developments have shown promise and it remains to be the cheapest, most environment-friendly, and most effective way of dealing with oil spills

Simulated transport of silver therapon (Leiopotherapon plumbeus) fingerlings at different durations and loading densities: Effects on survival and water quality

The silver therapon, Leiopotherapon plumbeus, is being promoted as a new species for aquaculture. However, information on the optimal conditions for the transport of this species for grow-out culture needs to be established to avoid stress and unnecessary mortalities. This study examined the effects of duration of transport and loading density on survival and water quality during simulated transport of silver therapon (Leiopotherapon plumbeus). Hatchery-produced fingerlings [1.30±0.34 g body weight (BW); 44.30±3.77 mm total length (TL)] were held in double-layered oxygenated plastic bags at three transport durations (6 h, 9 h, and 12 h) and densities (40 fish bag-1, 80 fish bag-1, and 120 fish bag-1) in triplicates. Mean survival rates were not significantly affected by both duration of transport (P=0.321) and loading density (P=0.345). However, a highly significant effect of duration of transport on dissolved oxygen (DO) and pH (P=0.000), and a significant effect on Total Ammonia Nitrogen (TAN; P=0.039) and total bacterial count (TBC; P=0.034) were evident. Similarly, water quality parameters were significantly influenced by loading density (P=0.000), with lower DO and pH levels, and higher TAN and TBC recorded at 120 fish bag-1 density. Since a very high survival rate (>99%) is achieved at the highest loading density of 120 fish bag-1 up to 12 h transport, this density can be recommended to transport silver therapon fingerlings. However, chemical treatments using either salt, methylene blue, or tropical almond leaf extract in transport water may be used to reduce the high bacterial count during transport.This study was supported by the SEAFDEC Aquaculture Department (Br-02-F2015B). The authors thank M. J. Reyes, J. C. Unida, J. dela Cruz, Jr., R. Lazartigue, R. Celebre and N. Olorvida for counting and packing the fingerlings

Population genetic variation and genetic structure of widely distributed Japanese endemic freshwater crustaceans: Geothelphusa dehaani and Gammarus nipponensis

Freshwater crustaceans, Geothelphusa dehaani (White 1847) and Gammarus nipponensis (Ueno 1940), are commonly found in rivers, streams and lakes in Japan. The distribution range of G. nipponensis is concentrated in the Western portion of Japan while G. dehaani exhibits a more widespread distribution. Both species undergo direct development from eggs to juveniles and have limited migratory abilities, as they are intolerant to brackish and marine environments. This restricted dispersal capability leads to geographical isolation among populations, making these freshwater crustaceans as ideal models for studying gene flow. Despite their significance, there were scarcity of studies that clarified genetic patterns in these two widely distributed crustaceans. Thus, the objectives of this thesis were to conduct genetic assessments on both G. dehaani and G. nipponensis to understand their population structure and variation, and to provide insights into past geological events that have contributed to these variations. Here, mitochondrial DNA sequence data were utilized to infer the relationships between the local populations of these species. Results of this study revealed substantial genetic variations among populations in both crustaceans. In G. dehaani, distinct haplotypes were observed in most populations, while G. nipponensis exhibited remarkably high mitogenome sequence variability across different localities. These findings implied extremely limited gene flow within each population and a reduced capacity for migration over extended periods, a characteristic that distinguishes them from other strictly freshwater species. The time to most recent common ancestor (TMRCA) estimates proposed that the ancestor lineage of G. dehaani was introduced more recently in Japan, approximately around the Pleistocene (~1 million years ago), while that of G. nipponensis predates the separation of Japan from mainland Asia around late Oligocene (~24 million years ago). Despite these differences, the structural patterns of populations in both species appeared relatively similar. Based on the phylogenetic analysis, the populations in both species are considered highly monophyletic with several geographical groups detected. In G. dehaani, four distinct geographic groups formed: Clade I (Honshu and Shikoku), Clade II (Eastern Kyushu), Clade III (Southern Kyushu and a portion of Eastern Honshu) and Clade IV (Western Kyushu). In G. nipponensis, the three identified groups were Clade I (Honshu and Shikoku), Clade II (Eastern Kyushu) and Clade III (Western Kyushu). The geological boundaries separating these major clades consisted of ancient lowlands such as the present Seto Inland Sea and the Chikushi and Fukuoka plains, acting as barriers for gene flow. The Seto Inland Sea potentially contributes to the divergence of Clade I from the Kyushu group. Despite the Seto Inland Sea acting as a barrier, Honshu and Shikoku displayed closer genetic relationships, possibly attributed to their more recent separation. Likewise, the Chikushi and Fukuoka plains was a significant barrier, defining distinct genetic groups in Kyushu. In conclusion, this study emphasized the importance of these two freshwater crustaceans in understanding genetic relationships characterized with limited gene flow and the impact of geological events on their population dynamics in the Japanese Archipelago. The need for further examination of morphological and behavioral characteristics based on the genetically detected groups of G. dehaani and G. nipponensis is suggested