Milkfish Farming Research Articles

PROFIT EVALUATION OF MILKFISH DOWNSTREAM SUPPLY CHAIN FOR LOCAL MARKETS: SYSTEM DYNAMIC APPROACH

Milkfish is an aquaculture product and has a role in supporting food security and nutrition in Indonesia. The reliability of milkfish farming will be able to increase the income of small and medium-scale farmers. Milkfish farmers in SMEs level experience problem of declining prices in the period of oversupply in farming. Moreover, the profit earning by the farmers tend to decrease time to time. This research was mapping the structure of milkfish downstream supply chain using system dynamic simulation. The first step in mapping process was identifying the actors in the milkfish downstream supply chain. The next stage was defining activities and variables that affect supply chain milkfish profit. The activities and variables were used to develop a causal loop diagram (CLD). Furthermore, stock and flow diagram was constructed based on CLD and used as system dynamic simulator of milkfish supply chain. The result of system dynamic simulation showed the profit obtained by each actor in milkfish supply chain and a total profit of the entire supply chain. The profit, gained by supply chain in the current configuration, during the period 2016-2020, is Rp72.615.608.004,00. According to the simulation result, the proposed scenario will be able to increase the profit of supply chain up to 27,58%.

Utilization of Displaced Land of Former Red Stone Excavation for Milkfish Farming by Stick Net Cage System (A Case Study at Gentungan, Gowa Regency, South Sulawesi, Indonesia)

This study was conducted at Gentungan village, West Bajeng District, Gowa Regency, South Sulawesi Province, Indonesia for four months, i.e., from March to July 2016. The study aimed to (1) determine the feasibility of water quality for nursing at the former land of red stone excavation, (2) analyze the growth rate, and (3) analyze the survival rate. Method used in this study was the stick net cage system which sized 4.0 × 3.0 × 1.5 m, with an average density was 20 fish/m3. The results showed that (1) the measurement and analysis results of water quality during the nursering period were still in the limits of feasibility as presented in Table 1, (2) the analysis results of growth rate were obtained an average growth rate of 117 gram for 160 days, and (3) the survival rate was 86%.

Production and Efficiency of Pond Fish Farming Business Milkfish

Various different factors, either direct or indirect one, contribute to decreasing production of milkfish in milkfish farms located in North Konawe. Production of milkfish in the area is relatively low and it is predicted that the milkfarmers’ inability to either allocate inputs or maximize the use of the inputs becomes the cause. Therefore, the objectives of the study were to analyze the line of production factors and production efficiency of milkfish farm in South Konawe. Path analysis was the method to analyze the direct and indirect factors affecting the production of the milkfish farm while marginal product value was the one used to analyze the price efficiency and optimal input. The findings of the study indicated that: the factors that directly affected production were the number of seed and employees as well as the amount of fertilizer while the factors indirectly affecting production were the number of seeds and employees as well as the amount of fertilizer. The milkfish farms in North Konawe would become efficient when there were 7,606 milkfish seeds, 41 employees and 427 kilograms of fertilizer.

ANALISIS USAHA BUDIDAYA TAMBAK BANDENG PADA TEKNOLOGI TRADISIONAL DAN SEMI_INTENSIF DI KABUPATEN KARAWANG

The low productivity of milkfish produced by traditional technology encourage the development of new farming technologies to increase productivity. Semi-intensive technology has evolved since the 2000s. However, this technology increases the cost of production because of the additional input of artificial feed. One of the regencies which produce milkfish using both traditional and semi-intensive technology is Karawang Regency. The objective of this research were to analyze profit and cost efficiency in traditional and semi-intensive techonology. The method of data collection conducted purposive as many as 30 milkfish farmers with traditional technology and 33 milkfish farmers with semi-intensive technology. The results show that semi-intensive technology provides a higher level of productivity and higher profitability. However, traditional technology was more efficient than semi-intensive technology. This condition causes the milkfish cultivation with traditional technology are still exist because it provides a higher return to capital.

Pemberdayaan Masyarakat melalui Pengembangan Polikultur Bandeng dan Udang di Desa Karangsong, Indramayu, Jawa Barat

Karangsong Village is one of the coastal villages in Indramayu which has a high fishery and marine resources potential, (both capture and aquaculture fisheries). The aquaculture activities in this village were mostly milkfish and prawn cultures. Community development through polyculture activity in this village had been done for 2 years 4 months from December 2012 to April 2015. This activity aimed to improve the community skill, especially milk fish and prawn using polyculture system. Methode used in this activity was training and empowering. The community was trained about pond culture preparation and milk fish and prawn culture methods. The community participated in first year was 4 people, and second year was 9 people. Aid distribution scheme of this program was 1 package for each fish-farmer contained prawn seed, milkfish seed, and fish-prawn feed. Through effectively empowering program, people knowledge, technology, biomass farming, and income (912 million from milkfish farming; 920 million from shrimp farming) were increased.

Community Based Milkfish Farming in Tanzania

In the 1990s experimental integrated mariculture of finfish, shellfish and seaweeds in a flow through system was developed to investigate bio-filtration in the ponds. The project supported mainly by WIOMSA culminated in a stakeholders’ workshop in 2004 translating the results of the experiment to community based projects. The finfish tested were milkfish ( Chanos chanos ), rabbit fish ( Siganus canaliculatus and S. sutor ), mullet ( Mugil cephalus ) and Zanzibar tilapia ( Oreochromis urolepis hornorum ). Before the workshop there were 3 milkfish mariculture ponds in Tanzania one of which was established by IMS. Following the workshop, pond finfish mariculture took off in the coastal Tanzania. In 2006, the first commercial type farm at Bagamoyo produced 1 MT/ha/yr, earning the group 2000 USD. Ever since, finfish farming has spread to all coastal districts with the highest production of 7.5 MT/ha/yr at Ndumbwe Mtwara in 2011. In 2011, trials of tilapia acclimatization and farming in estuarine and full strength sea water were started where survival and growth rates of fry and fingerlings of 4 species of tilapia were tested.

Bacterial community composition of sediments from a milkfishChanos chanosForsskål farm

Bacterial communities in sediments underneath milkfish cages and adjacent off-cage areas in Bolinao, Lingayen Gulf, West Philippine Sea were characterized using PCR-denaturing gradient gel electrophoresis to assess influence of the fish farming to the sediments. The sediments in the fish cage (FC) area showed anoxic conditions [redox potential of −165 to −213 mV and acid-volatile sulphide-sulphur (AVS-S) of 0.55–1.88 mg g−1 (dry weight)] compared to the relatively oxic off-cage area [redox potential of 72–81 mV and AVS-S of 0.09–0.14 mg g−1 (dry weight)]. The composition of the microbial populations revealed influence of the fish feed sedimentation with higher dominance of putative sulphate-reducing bacteria (SRB) in the FC area. Compositions of the bacterial taxa showed dominance of the Bacteroidetes group and Deltaproteobacteria. The results suggest that the fish feeds created a new suitable environment, in which reductive microorganisms such as SRB, ferric-ion-reducing bacteria and nitrate-reducing bacteria can thrive. Organic load from the feed and quantity of its leftover constituents may be the key factors that influence the structure of the bacterial community in the sediments of the milkfish farms.

Diet, growth, and abundance of two seagrass bed fishes along a pollution gradient caused by milkfish farming in Bolinao, northwestern Philippines

The present study clarified the impacts of aquaculture pollution on the surrounding seagrass bed fishes by comparing the diet, growth, and abundance of Parupeneus barberinus and Acreichthys tomentosus along a pollution gradient caused by intensive milkfish Chanos chanos farming in Bolinao, northwestern Philippines. The two fish species and potential food items exhibited increasingly enriched δ13C values with greater distance from the milkfish farming area, thereby indicating that stable carbon isotopes facilitated good discrimination between fishes from polluted and unpolluted areas. P. barberinus fed on epi-/benthic crustaceans, whereas A. tomentosus consumed a wide range of food, including invertebrates and plant materials in the unpolluted areas, but zooplankton were the most commonly predated food items in the polluted areas for both species. The growth rate of P. barberinus was marginally lower in the polluted area than in the unpolluted area, whereas that of A. tomentosus did not differ between the two areas. The abundance of both species did not differ significantly between the polluted and unpolluted areas, but the growth patterns of the two species suggest that A. tomentosus has greater physiological tolerance of the polluted environment than P. barberinus.

Response of Trophic Groups of Macrobenthos to Organically Enriched Sediments: A Comparative Study between Temperate and Tropical Regions

This study is aimed to detect the level of environmental disturbance caused by farming activities using trophic groups of macrobenthic assemblages, with emphasizes the difference between temperate and tropical regions. The samples of macrobenthic assemblages were taken from 2 (two) farm sites, i.e. Southern Spencer Gulf, South Australia, where farming of southern bluefin tuna ( Thunnus maccoyii ) takes place, representing as a temperate region (Site I) and milk fish ( Chanos chanos ) farms and mangrove area at coastal region of Mngkang Kulon, Semarang, Central Java, Indonesia, representing as a tropical region (Site II). Macrobenthic abundance was categorised based on six major trophic groups. Macrobenthic assemblages dominated by all polychaetes, they are Capitellidae, Cirratullidae, Lumbrineridae, Nephtyidae, and Spionidae at Site I (temperate region), owing to their relatively tolerance to organic enrichment, both at the farm sites and at control sites. Surface deposit feeders (SDF) dominated in abundance at both control and fish farm sites at Site I, whilst subsurface deposit feeders (SSDF) exhibited highest in proportion at Site II over the study period, in particular species of Capittelidae, indicating that both sites has been influenced by fish farm activities. The abundance of deposit feeders was significantly higher at the farm sites than at the reference sites. Organic carbon in the sediment surface is likely to correlate with deposit feeding and sub-surface deposit feeding species richness, whereas total and food particulate matter correlate with species diversity. The result of this comparative study implies that response of trophic groups of macrobenthos to environmental disturbance are considerably similar at both tropical and temperate regions.

Impact of milk fish farming in the tropics on potentially pathogenic vibrios

Ratios of sucrose-negative to sucrose-positive vibrios on TCBS agar (suc−/suc+) indicate the abundance of potential human pathogenic non-cholera vibrios in coastal mariculture environments of the Lingayen Gulf (Philippines. In guts of adult maricultured milkfish (Chanos chanos) of suc− vibrios reached extreme peak values ranging between 2 and 545millionperg wet weight. Suc− vibrios outnumbered suc+ vibrios in anoxic sediments, too, and were rarely predominant in coastal waters or in oxidized sediments. Suc−/suc+ ratios in sediments increased toward the mariculture areas with distance from the open sea at decreasing redox potentials. There is circumstantial evidence that suc− vibrios can be dispersed from mariculture areas to adjacent environments including coral reefs. An immediate human health risk by pathogenic Vibrio species is discounted, since milkfish guts contained mainly members of the Enterovibrio group. A representative isolate of these contained proteolytic and other virulence factors, but no genes encoding toxins characteristic of clinical Vibrio species.

Enzymatic degradation of proteinaceous compounds in sediments exposed to intensive mariculture in the tropics

Anoxic and sulfidic sediments formed during intensive milkfish farming in Bolinao Bay (Lingayen Gulf, Luzon, Philippines) showed concentrations of total proteinaceous matter roughly three times higher (up to16.9 mg cm−3) than those of less reduced sediments. Ectoprotease activities in these coastal sediments suggested an inhibition of enzymatic recycling of proteins by sulfide. Sodium sulfide proved capable of inhibiting protease activity produced by a bacterial isolate from a sulfidic sediment site (Ki = 20 mM Na2S · 9H2O). Reoxidation and removal of H2S from sulfidic sediments, however, proved inadequate to recover proteolytic activity. Hence, H2S formed during organic matter mineralization via bacterial sulfate respiration may have initiated an irreversible inhibition of the enzymatic degradation of proteinaceous matter from fish farming. Ectoprotease activity was positively correlated (r = .93) with redox potential values. Lowest proteolytic activities were found in strongly reduced sediments, that were predominantly fine grained (very fine sand and silt) and sulfidic at the same time. Low ectoprotease activity in these sulfide-rich sediments can be interpreted as a kind of negative feedback mechanism that would mitigate the immediate recycling of excessive amounts of feed borne protein-rich deposits. Proteins may be further protected from degradation by selective particle adsorption in the finest grained deposits of fish farming waste.

Impact of polychaete infauna on enzymatic protein degradation in marine sediments affected by intensive milkfish farming

Marine sediments at intensive fish farming sites in Bolinao-Anda, northwestern Philippines, are characterized by strong oxygen depletion and the widespread predominance of sulphidic conditions precluding macrobenthic infauna. In less affected areas, however, small macrobenthos (Spionide polychaetes) was present. Experimental sediment mesocosms containing burrowing polychaetes were set up to investigate the possible links between macrofaunal bioturbation of the sediment and its proteolytic capacity to recycle protein-rich fish farming waste. Relative to polychaete-free sediment, the addition of small Spionide polychaetes had no significant effect on the proteolytic capacity but caused an increase in the redox potential. On the other hand, the addition of large Eunicide polychaetes caused an increase in both the proteolytic capacity and the redox potential. The deposition of commercial fish feed particles increased the proteolytic activities but decreased the redox potential particularly at a higher deposition rate (250 g m⁻² day⁻¹). Accumulation of hydrogen sulphide increased at deposition rates above 83 g m⁻² day⁻¹ and limited the survival of large polychaetes.

Gradients of coastal fish farm effluents and their effect on coral reef microbes

Coastal milkfish (Chanos chanos) farming may be a source of organic matter enrichment for coral reefs in Bolinao, Republic of the Philippines. Interactions among microbial communities associated with the water column, corals and milkfish feces can provide insight into the ecosystem's response to enrichment. Samples were collected at sites along a transect that extended from suspended milkfish pens into the coral reef. Water was characterized by steep gradients in the concentrations of dissolved organic carbon (70-160 microM), total dissolved nitrogen (7-40 microM), chlorophyll a (0.25-10 microg l(-1)), particulate matter (106-832 microg l(-1)), bacteria (5 x 10(5)-1 x 10(6) cells ml(-1)) and viruses (1-7 x 10(7) ml(-1)) that correlated with distance from the fish cages. Particle-attached bacteria, which were observed by scanning laser confocal microscopy, increased across the gradient from < 0.1% to 5.6% of total bacteria at the fish pens. Analyses of 16S rRNA genes by denaturing gradient gel electrophoresis and environmental clone libraries revealed distinct microbial communities for each sample type. Coral libraries had the greatest number of phyla represented (range: 6-8) while fish feces contained the lowest number (3). Coral libraries also had the greatest number of 'novel' sequences (defined as < 93% similar to any sequence in the NCBI nt database; 29% compared with 3% and 5% in the feces and seawater libraries respectively). Despite the differences in microbial community composition, some 16S rRNA sequences co-occurred across sample types including Acinetobacter sp. and Ralstonia sp. Such patterns raise the question of whether bacteria might be transported from the fish pens to corals or if microenvironments at the fish pens and on the corals select for the same phylotypes. Understanding the underlying mechanisms of effluent-coral interactions will help predict the ability of coral reef ecosystems to resist and rebound from organic matter enrichment.

Distribution and bioturbation effects of the tropical alpheid shrimp Alpheus macellarius in sediments impacted by milkfish farming

The impact of milkfish fish pens on the distribution of the alpheid shrimp Alpheus macellarius was studied in the Bolinao area, Philippines. In addition, the impact of the alpheid shrimp on sediment biogeochemistry, including organic matter mineralization, nutrient and sulfur cycling was compared in sediments affected and unaffected by fish farming. The fish farming activity had negative impact on the distribution of shrimps by reducing the abundance up to 60% in the vicinity of the net pens, and to almost absence inside the net pens. At a farm site abandoned seven month prior to sampling the abundance of shrimps was still low and sediment pools of reduced sulfur high, indicating a slow benthic recovery. The shrimp had large physical impact on the sediments, and the mineralization rates were stimulated by the presence of the shrimp in pristine sediments, whereas the fish farm impacted sites showed high mineralization rates both in sediments with and without the presence of the shrimp suggesting that the organic matter enrichment stimulated the mineralization in these low-organic sediments, whereas the shrimp had less impact. Sulfate reduction rates and in particular pools of sulfides increased in the farm impacted sediments, and sulfate reduction was an important process for organic matter mineralization (>67%) in all sediments. Although the shrimp had minor effect on the organic matter mineralization and nutrient fluxes in the farm impacted sediments, they appeared to increase the oxidation of sulfides by increasing the zone of oxidized surface sediment and thereby improving the sediment conditions for recolonization after fish farming has ceased.

AN EMPIRICAL TYPOLOGY OF BRACKISH-WATER POND AQUACULTURE SYSTEMS IN THE PHILIPPINES: A TOOL TO AID COMPARATIVE STUDY IN THE SECTOR

Aquaculture in the Philippines is long-established but has witnessed rapid technical change in the last 20 years with the introduction of hatchery technology and commercial feed mills changing the production possibilities for a fishpond operator. To understand the sector, a typology of brackish-water pond farming systems is constructed using multivariate methods (principal components analysis, cluster analysis). Eight input variables across all major factors of production are used in the analysis, gathered from a net sample of 136 farms in two regions in 2003. Three latent variables are described, accounting for 58% of variance in the original data: specialization; land vs. labor intensity; and feeding intensity. Five clusters (farm types) are subsequently described: extensive polyculture (40% of sample); semi-intensive prawn-oriented polyculture (11%); low-input labor-intensive farms (27%); very large, extensive milkfish-oriented farms (8%); and semi-intensive milkfish monoculture farms (14%). Implications for technical efficiency estimation and comparative study of economic indicators are discussed.

Hatchery-Produced Milkfish (Chanos chanos) Fry should be Fed Docosahexaenoic Acid-Enriched Live Food: A Case of the Difficulty in the Transfer of Improved Aquaculture Technology in the Philippines

Levels of highly-unsaturated fatty acids, the most important nutritional factors in fry production of marine fish, were compared between hatchery-produced and wild-caught milkfish Chanos chanos fry. The most striking difference found between the fry was in docosahexaenoic acid (DHA: 22:6n-3) levels: DHA levels in hatchery-produced fry were only 37% and 18% of those in wild-caught fry in the polar lipids and neutral lipids, respectively. However, high DHA levels were detected in ovary and spawned eggs from hatchery-reared broodstock. Investigation on the time course change in DHA levels of hatchery-produced fry revealed that the DHA levels of polar lipids drastically declined from 25% at day 0 posthatching to 5% at day 14 posthatching. Nannochloropsis sp. and rotifers Brachionus sp., which were used as live food from day 2 to day 14, did not contain DHA with relatively high eicosapentaenoic acid (EPA: 20:5n-3) levels. DHA level was restored to 13% in 45-day old fry by feeding of formulated diets with a substantial amount of DHA from day 15. Thus, the lack of DHA in the live food appears to lead to the low DHA level in hatchery-produced fry. On the other hand, the cost of DHA enrichment for one milkfish fry was estimated to be 2.6 Philippines centavos, which is equivalent to about 10% of the market price of milkfish fry. The increase of the production cost might not be accepted in domestic hatcheries under competitive marketing with imported fry. Financial and marketing support by the government will be one of the measures to encourage the stable production of domestic milkfish fry with high quality in the Philippines. It is also necessary to conduct institutional campaigns to inform local fry producers and milkfish farmers of the importance of DHA-enrichment.

Technical efficiency analysis of milkfish (Chanos chanos) production in Taiwan—an application of the stochastic frontier production function

Milkfish has been farmed in Taiwan for over 300 years. Faced with limited land resources, a labor shortage, decreasing demand, and growth of imported fisheries products, the industry is looking at the problem of how to maintain a sustainable and efficient production. This study specifies a stochastic production frontier function to estimate potential milkfish farm output and efficiency by using 1997–1999 data from a survey of 433 aquaculture milkfish farms. Both Translog and Cobb-Douglas frontier production models are estimated using the maximum likelihood estimation method. Empirical results show that the Translog stochastic production function model fits the data better and that milkfish farming in Taiwan exhibits diminishing returns to scale. We also compare estimated maximum potential milkfish production per hectare under various pond conditions to provide managers with information about how to boost efficiency. In addition, this study estimates substitution elasticities and complementarity of input factors for milkfish farms to provide helpful information for milkfish farmers on how to reallocate input resources and help raise milkfish productivity through improvements in technical efficiency.

From triphenyltins to integrated management of the pest' snail Cerithidea cingulata in mangrove-derived milkfish ponds in the Philippines

The potamidid snail Cerithidea cingulata is considered a pest in brackishwater milkfish ponds in the Philippines and has been controlled by the triphenyltin (TPT) compounds Aquatin and Brestan. But TPT is also toxic to other invertebrates, fishes, algae, bacteria and people, and high TPT residues occur in sea foods including milkfish. Thus, control of snails in milkfish ponds should be shifted from reliance on TPT to an integrated pest management (IPM) strategy. To formulate a responsible IPM, studies were conducted on C. cingulata in ponds and mangroves and the available data were synthesized with the relevant information from the literature. The deposit-feeding C. cingulata is a native resident of mangrove areas and becomes a problem in mangrove-derived ponds where the lack of competitors and predators results in 'ecological release' and population explosion. Snail densities ranged 1–470 m−2 in the mangroves and 100–5000 m−2 in ponds. In ponds, snails ranged 2–40 mm in shell length; those 25 mm long and 8 mm wide weighed 1 g on average, and had 150 mg flesh. Snails matured at 20 mm long and reproduced the whole year with a peak in Mar–Sep at water temperatures of 24–36 °C. Enriched sediments and stagnant water in ponds allowed fast growth and reproduction, low dispersal and high recruitment of snails. Snails were very tolerant to hypoxia and adverse conditions, but were killed within a week by sun-drying or by salinities of 48–70‰ and within 3 d by ammonium phosphate at 10 g l−1 or urea at 5 g l−1. IPM of snails requires changes in mind sets and perspectives of milkfish farmers and industry supporters and changes in farm practices and management. Snails must be viewed as a resource from which income can be made and employment can be generated. Harvest of snails for shellcraft and other enterprises also effectively removes the spawning population. Complete draining and sun-drying of ponds after harvest kills the adult snails and the egg strings on the bottom. Snails in puddles in the ponds may be killed by the usual nitrogen fertilizers and lime applied during pond preparation. Water input may be timed with periods of low veliger counts in the supply water. These IPM recommendations have yet to be verified.

The effect of stunting on growth, survival, and net production of milkfish ( Chanos chanos Forsskal)

The seasonal abundance of milkfish fry in the Philippines has led to the practice of buying a sufficient supply during the peak season to compensate for the shortage during slack periods. Fry that are not immediately grown out are crowded and stunted in transition ponds until they are transferred to rearing ponds. Milkfish farmers believe that stunted fingerlings grow faster than newly grown ones and therefore yield extra croppings. To assess the efficiency of production schemes, stunted and non-stunted milkfish fingerlings were cultured in twelve 144-m 2 ponds for a 3-month period. The treatments employed were: Treatment I, 2-month-old fingerlings; Treatment II, 3-month-old fingerlings; and Treatment III, 6-month-old fingerlings, with the initial weights of 3.3 g, 7.8 g, and 43.1 g, respectively. Survival, net production, cumulative and monthly weight gains did not differ significantly ( P > 0.05) among the three treatments. The results indicate that stunting did not illicit a significant increase, nor did it adversely affect the growth, survival, and net production of milkfish in a straight culture system. Stunting can therefore be practised by farmers to provide an adequate supply of fingerlings for year-round operation.

REPORT ON THE INDUCED MATURATION AND OVULATION OF MILKFISH (Chanos chanos) REARED IN TANKS1

ABSTRACTThe milkfish (Chanos chanos [Forskal]) is one of the most important cultivation fishes in Southeast Asia. Since 1970, Tungkang Marine Laboratory (TML) has embarked on a long‐term program in broodstock maintenance and artificial propagation with the goal of supplying adequate fry for milkfish farming. In the past three years, the histological study of gonadal development and the experiment on inducing maturation and ovulation of adult milkfish with hormonal injections were carried out. It was found that 5‐ or 6‐year‐old tank‐reared fish could reach full maturity after hormonal treatment. Sperm were always found in males with Gonadal Somatic Index (GSI) larger than 0.20, with or without treatment. All of the ovarian oocytes of three female spawners with GSI of 11.23, 8.12 and 10.70 reached mature stage after treatment, and average diameter of the eggs was 1.16, 0.94 and 1.19 mm, respectively. One female spawned naturally after one injection, and released hydrated eggs measuring 1.08 mm in diameter. However, the eggs were not fertilized.Pituitary gland homogenates of both salmon and mullet, human chorionic gonadotropin (HCG), and Puberogen plus vitamin E used in the present experiment seemed more effective in stimulating gonadal development when ovarian oocytes were beyond the tertiary yolk stage, i.e., the oocyte sizes were larger than 0.70 mm in diameter.Although most of the treated females failed to ovulate, they were still prospective spawners. The success of artificial propagation with tank‐reared spawners is anticipated in the near future.