Growth variations within a farm of mussel (Mytilus galloprovincialis) held near fish cages: importance for the implementation of integrated aquaculture

Fish farming releases extensive amounts of particulate organic waste that can be exploited by bivalves in integrated culture. We tested if mussels Mytilus galloprovincialis cultured at two depths (1 and 6 m) in a raft, moored 170 m from a fish farm had greater growth than bivalves held 550 m from the fish cages. Mussel growth was monitored monthly, covering the second phase of the culture, from thinning‐out to harvest (March to November 2011). We also studied if fish solid and dissolved nutrients increased the organic content of the seston and chlorophyll‐a levels near the fish cages through weekly samples. Results showed no differences in seston, chlorophyll and physiochemical characteristics of the water among rafts. Maximum growth and Condition Index (CI) occurred during spring–summer (April–August), when mussels had access to greater food quality and quantity. Mussels cultivated close to the cages showed similar shell length, weight and CI compared with mussels distant from the fish farm. Average shell length, meat dry weight and CI at harvest were 76.31 mm, 2.51 g and 23%. Bivalves cultured distant from the fish cages displayed 26% higher biomass than the other raft at the end of the experiment. Differences in biomass were explained by the significantly higher recruitment of mussel seed observed at the raft distant from the fish cages from June to November. The lack of a significant enhancement in growth of the bivalves cultured next to finfish is discussed.     

Effects of marine fish farming on nutrient composition and plankton communities in the Eastern Aegean Sea (Turkey)

The hypothesis that the presence of fish farming zones affects the water quality and plankton communities was investigated in an Aegean Sea fish farm during February, June, September and January 2000–2001. In the spatial coverage, a total of 12 stations were sampled; three of them were reference stations. A variance analysis was applied to the measurements made at the stations near the fish farms and at the control stations. While no significant differences in concentrations of nutrients, chlorophyll a, particulate organic carbon and particulate organic nitrogen were detected between the stations and the control sites within one season, significant differences were detected between the parameter values measured except for total dissolved phosphorus and dissolved organic phosphorus at different seasons. The seasonal differences were also significant with regard to the biodiversity. Together with these temporal differences in general, there was a higher diversity of species at the control site as compared with the other stations in September, which was the key season to detection of significant changes. The most important consideration is that it is not sufficient to take the instantaneous values for the physico‐chemical variables; rather, it is necessary to monitor the biological parameters in order to define the differences in the ecosystem.     

Occurrence and prevalence of infectious pancreatic necrosis virus in rainbow trout (Oncorhynchus mykiss) cultured in cages in the Black Sea

Rainbow trout (Oncorhynchus mykiss) cultured in cage systems in the South Eastern Black Sea were surveyed for the type, occurrence and prevalence of infectious pancreatic necrosis virus (IPNV). Two nearby farms (designated as Farm A and Farm B) were visited monthly in 2007 and 2008. At each farm, 385 fish were selected randomly from five cages. Another farm with infected trout from a hatchery also was monitored for IPNV from the transfer to harvest. IPNV was found to be prevalent in both farms surveyed. In Farm A, IPNV was present throughout the growing period, from January to May, and all five randomly sampled cages tested positive for IPNV in March and April of 2007. In Farm B, IPNV was present only in February and March in 2007, and in 2008, IPNV was observed in January (two cages) and February (one cages) at low levels. Interestingly, IPNV was absent 2 weeks after transfer to the sea at 17.5°C. The same strain of IPNV, genotype III that was isolated from the same stock of fish at the hatchery, reoccurred when water temperatures dropped to 12°C in December in the Black Sea. Transferring fish to the sea at high water temperatures could lessen the negative impacts of IPNV on growth of rainbow trout in brackish water.     

Assessment of infectious salmon anaemia virus prevalence for different groups of farmed Atlantic salmon, Salmo salar L., in New Brunswick

Abstract Infectious salmon anaemia (ISA) virus (ISAV) has been causing disease in New Brunswick since 1996. As a control measure, all fish in an outbreak cage are killed. The objective of this study was to compare ISAV prevalence in cages experiencing an outbreak with healthy cages from the same farm, neighbouring farms and distant farms. Atlantic salmon from five different groups were tested using an RT-PCR test. Groups included moribund fish from a cage experiencing an outbreak (A), healthy fish from an outbreak cage (B), healthy fish from a negative cage from a farm experiencing an outbreak in a different cage (C), healthy fish from a negative farm near an outbreak farm (D), and healthy fish sampled at a negative farm located in an area with only negative farms (E). Apparent prevalences (standard error) for the different groups (A-E) were 0.94 (+/-0.026), 0.41 (+/-0.062), 0.29 (+/-0.040), 0.08 (+/-0.037) and 0.08 (+/-0.037), respectively. All groups were significantly different (P < 0.002) from each other except for groups B and C and groups D and E. Because the prevalence of the virus was significantly higher in the outbreak cage (B) compared with other sites, early harvest of outbreak cages will remove one source of virus. However, ISA negative cages (C) that remain on the positive farm may potentially act as a viral reservoir.     

Environmental conditions at sea-cages, and ectoparasites on farmed European sea-bass, Dicentrarchus labrax (L.), and gilt-head sea-bream, Sparus aurata L., at two farms in Greece

Water quality in sea-cages, and metazoan ectoparasites on bass, Dicentrarchus labrax (L.), and bream, Sparus aurata L., were sampled at two fish farms in south-west Greece over 2 years. The seabed and marine life around the cages of one farm was surveyed using scuba. The most frequent and abundant parasites were the monogeans Sparicotyle chrysophrii and Furnestinia echeneis on the gills of bream, and Diplectanum aequans on the gills of bass. The copepod Caligus minimus occasionally occurred in the buccal cavity of bass, but only in low numbers. Prevalence and abundance of parasites increased with bass size but F echeneis levels decreased with bream size. There were no other clear relationships between water quality, parasite levels and fish size. Ammonia varied seasonally with sea temperature, and with oxygen levels below 6 mg 1^-1 on many occasions, it is possible that fish suffered stress from a combination of high ammonia and low oxygen conditions. There was no accumulation of waste food or faeces below the cages at the one farm surveyed, but there were thousands of wild fish, including mullet (Mugilidae), Spicara sp. and Diplodus spp., present around the cages. Water quality may be improved by changes in farm management, such as reducing stocking densities below the present 16 kg nr^-3. Oxygen should be monitored at the cages on site daily. How comparable environmental conditions and impacts, and parasitization are at other bass and bream sea cage farms is unknown.     

Hydrodynamic implications in and around a caged finfish farm and its implications on the dispersal of farm debris

One of the key factors in determining the accumulation of sediment and soluble nutrients within a lease is water movement. Water masses entering and leaving the farm determine the finfish ecosystem interaction. Understanding the hydrodynamic interaction with the farm is therefore key to understanding the potential ecological effects of individual farms. In addition, finfish farms are now being proposed in exposed offshore environments and have caused concern regarding their potential down stream impacts on currents and wave climate. Seven current meters, oxygen probes and CTD were deployed to examine the hydrodynamic interactions inside and outside a 270 m long Salmon farm in Newfoundland, Canada. Current meter results indicate that the finfish farm cages have a clear shadowing effect on the currents. Currents upstream were found to be considerably faster than those recorded downstream during the sampling period. Current speeds inside the farm were also found to be considerably slower than those found outside of the farm especially during high flow events. In situ observations of currents were found to be similar to those predicted by previous CFD and hydrodynamic modelling studies. Modeling was also undertaken to calculate the energy lost as currents enter and leave a series of fish cages. In comparison to the observed flow the model compares relatively well. Flow recorded downstream of the farm was observed to be in the range predicted by the model as was the flow recorded inside and outside the cages. Current speed downstream of the farm is clearly affected by farm orientation which has important implications for the dispersal of farm debris. Average oxygen saturation within the cages over the 5 day sampling period was 80.2 %± SD 5.7 %, compared to nearly 100 %, 20 m and 50 m from the farm site. Orientation of the farm may play some part in determining the location and amount of oxygen depletion within the farm. The farm also acts to push water from deeper in the water column up into the cages which has implications for farms situated in heavily stratified environments.     

Salmon farming affects the fatty acid composition and taste of wild saithe Pollachius virens L.

There is an ongoing controversy on whether fish farming affects the quality of wild fish in fjords. In northern Norway, local people prefer not to eat saithe, Pollachius virens L., from areas in the vicinity of fish farms because they say the taste is inferior to saithe from other areas. To address this issue, saithe were collected in the vicinity of a salmon fish farm in a fjord in northern Norway and in two reference areas: one site 6 km away from the nearest fish farm in the same fjord, and the other in a fjord nearby with no fish farms. The objective of this study was to clarify whether the physiology or taste of saithe near fish farms differs from saithe in areas with no or limited influence from fish farms. The fish collected near farms were larger than those from control sites of the same age and had been eating pellets. Analysis of fatty acid composition of the fillet indicated that fish collected near the farms had fatty acid profiles that resembled that of pellets more than fish from reference sites. The results suggest that there were individual differences in the time spent near cages for saithe collected near the farm, and that saithe collected at the reference area in the same fjord had also been eating pellets, i.e. had visited at least one of the fish farms in the fjord. In a sensory test, the test panel found that saithe from the fjord without fish farms tasted better than saithe collected near the cages. The test panel found no clear differences in taste between saithe collected near the fish farm and saithe from the same fjord, but 6 km from the nearest fish farm.     

三峡库区支流小江回水区鱼类早期资源状况

2019年3-6月在三峡水库支流小江回水区开展了鱼类早期资源调查,以了解该区域仔稚鱼的种类组成、仔稚鱼密度的时间动态及其与环境因子的关系。结果显示：采集到12种仔稚鱼,以太湖新银鱼Neosalanx taihuensis、中华鳑鲏Rhodeus sinensis、子陵吻鰕虎鱼Rhinogobius giurinus、鲤Cyprinus carpio和鲫Carassius auratus仔稚鱼数量较多;4月下旬至6月上旬为仔稚鱼采集的高峰期,4月为鲤仔稚鱼密度出现高峰期,4-5月上、中旬为鲫仔稚鱼密度出现高峰期;底质类型、透明度和水温是影响所有种类、鲤和鲫仔稚鱼密度空间变动的最主要的因素。研究结果表明3-6月三峡水库水位的快速消落很可能是影响黏草产卵鱼类产卵孵化的关键影响因子,建议通过三峡水库的水位调度以及人工鱼巢在库区支流回水区的放置来缓解该影响。     

Comparative efficacy of trash fish versus compounded commercial feeds in cage aquaculture of Asian seabass (Lates calcarifer) (Bloch) and tiger grouper (Epinephelus fuscoguttatus) (Forsskål)

Trash fish/low valued fish is still the most commonly used feed in marine cage culture in Asia. Use of trash fish is controversial with regard to the sustainability of the farming practices, and related issues on environmental degradation. In this study, the results of farm based trials on Asian seabass (Lates calcarifer) and tiger grouper (Epinephelus fuscoguttatus) to evaluate the efficacies of the use of commercial pellet feed in comparison to trash fish/low valued fish in marine cages in Thailand are presented. In spite of the variations observed in each of the farm sites, the results indicate that the overall growth performances and fish survival rates between the two feed types were similar, for both species. However, better cost‐benefit and resource use were recorded for fish reared on trash fish/low valued fish. No significant differences were observed in water quality parameters, dissolved oxygen, transparency and ammonia, between sites where pellet or trash fish were used, inside and outside the cages and for both species. The results of the present study are discussed in the light of the current controversies on the use of trash fish/low valued fish in marine cage culture.     

Water quality and bacterial populations in a tropical marine cage culture farm

A study was conducted to investigate fluctuations in different physical and chemical parameters, and bacterial populations in a tropical marine cage culture farm for one annual cycle. Samples were collected from the centre of the farm (station 1) and away from the cages (station 2). There were no significant differences (P > 0.05) in water quality parameters, such as temperature, salinity, dissolved oxygen, conductivity and pH between the two stations during the neap and spring tides. Nutrient concentrations and bacterial counts were slightly higher at station 1 than station 2, but the differences were not significant (P > 0.05). In general, nutrients and chlorophyll a concentrations in the study area were higher than those reported in the pristine marine environment. There were significant correlations (P < 0.05) between some nutrients (soluble reactive phosphorus, nitrite and nitrate) and bacterial counts. There were no significant differences P > 0.05) in nutrient levels and bacterial populations between the neap and spring tides, probably because of the large number of farms operating in the shallow channel. The present study indicates that high organic loading from the fish farming activities could cause deterioration of the water quality in the cage-culture system as well as in the surrounding environment.     

Polychaetes as indicators of marine fish farm organic enrichment

Marine fish farms cause environmental disturbance of sediment due to uneaten food and fish faeces that accumulate on the sea bottom. These products give rise to organic enrichment followed by degradation processes; reduction of level of dissolved oxygen in the bottom water; generation of high levels of sulfides; changes of benthic assemblages and even azoic conditions. The soft bottom benthic communities and, above all, the polychaetes are considered good indicators of environmental perturbations considering their relatively fast changes in diversity and abundance and because their trophic flexibility and life-history traits are considered a pre-adaptation to the condition of disturbed habitats. The aim of the present study is to evaluate the polychaete population changes as a result of organic enrichment produced by a marine fish farm. The study was carried out on a fish farm located in the coastal water of Porto Ercole (Tyrrhenian Sea) with two submersible sea cages and a year production of 180 tonnes. The macrobenthos samples were collected during four campaigns (July and December 2001, May and October 2002). The results showed: 1) a rapid change of the assemblage located beneath the cages related to the fish biomass reared and a high dominance of the opportunistic Capitella spp.; 2) limited sediment disturbance close to cages (20–50 m); 3) no effect in the area 50 m beyond the cages. Two months after the fish harvest and thus reduction of organic enrichment, perturbated assemblages showed signals of recovery like species richness increase and reduction of opportunistic species.     

Characterization of intake and effluent waters from intensive and semi-intensive shrimp farms in Texas

Two commercial shrimp farms in south Texas were evaluated for influent and effluent water quality from June to October 1994. The intensive farm, Taiwan Shrimp Village Association (TSV) had an average annual yield of 4630 kg ha^?1 while the semi‐intensive farm, Harlingen Shrimp Farm (HSF), had a yield of 1777 kg ha^?1. The study had three objectives: (1) to compare influent and effluent water from the intensive and semi‐intensive shrimp farms, (2) to show which effluent water‐quality indicators exceeded allowable limits, (3) to indicate inherent problems in farms operated with water exchange and summarize how findings from this study led to changes in farms' management that limited potential negative impact on receiving streams. Water samples were collected and analysed twice a week for the TSV farm and once a week for the HSF farm. Samples were analysed for dissolved oxygen (DO), salinity, pH, ammonia‐nitrogen (NH₃‐N), nitrite‐nitrogen (NO₂‐N), nitrate‐nitrogen (NO₃‐N), total phosphorus (TP), total reactive phosphorus (TRP), five‐day carbonaceous biochemical oxygen demand (cBOD₅), total suspended solids (TSS) and settleable solids (SettSols). Most of the effluent constituents showed fluctuations throughout the sampling period often related to harvest activity. Effluent pH at TSV was lower than influent values but within the regulatory requirements set by Texas Commission of Environmental Quality (TCEQ), formerly known as Texas Natural Resource Conservation Commission (TNRCC). HSF effluent pH values were higher than its influent, but still within TCEQ limits. Effluent DO mean levels were generally below the regulatory daily mean requirement, with values at TSV often below those for influent. Effluent nutrient concentrations and net loads were generally higher at the intensive shrimp farm, with NH₃‐N mean concentrations above the daily mean set by the TCEQ on several occasions. Effluent TSS concentrations were higher than influent for both farms, with daily mean values above the TCEQ limit. The two farms presented similar TSS concentrations despite their different stocking densities. However, TSS total net load and net load per hectare were higher at the intensive farm. The semi‐intensive farm presented higher cBOD₅ concentrations and net loads despite its lower stocking density, with daily mean values above the TCEQ limit. The cBOD₅ net load at TSV presented negative values indicating higher load at the influent than at the effluent. Analyses showed no evidence of self‐pollution between influent and effluent at the two farms. The high feed conversion ratio (FCR) values (2.3 and 2.7 for the intensive and the semi‐intensive farm respectively) suggest that better feed management is needed to reduce nutrient and solid net loads release from the two farms. The data obtained from this study resulted in several modifications in design and management of the two farms that reduced the potential negative impact on receiving streams. A brief summary of the improvement in selected effluent water‐quality indicators at the intensive shrimp farm is provided.     

Fish assemblages of perennial floodplain ponds of the Sacramento River, California (USA), with implications for the conservation of native fishes

To assess the likelihood of enhancing native fish populations by means of floodplain restoration projects, habitat characteristics and fish assemblages of seven perennial floodplain ponds in Yolo Bypass, the primary floodplain of the Sacramento River, California (USA), were examined during summer 2001. Although all ponds were eutrophic, based upon high chlorophyll a or dissolved nutrient concentrations, relatively large shallow ponds generally exhibited higher specific conductivity and dissolved phosphorus concentrations than small deep ponds, which exhibited greater water transparency and total dissolved nitrogen concentrations. Using multiple gear types, 13 688 fishes comprising 23 species were collected. All ponds were dominated by alien fishes; only three native species contributing <1% of the total number of individuals and <3% of overall biomass were captured. Fish assemblage structure varied among ponds, notably between engineered vs. natural ponds, and was related to specific conductance, total dissolved solids and water transparency.     

补远江鱼类多样性研究

根据澜沧江下游一级支流补远江2006年鱼类洄游季节3～6月的采样数据,分析了该流域鱼类多样性,并结合同期水文、水质数据,应用人工神经网络分析环境因子与鱼类多样性的关联。结果表明,2006年3～6月共采集补远江鱼类34种,隶属于3目8科22属,其中有8种洄游鱼类。3月份多样性指数最高,各月均匀度指数无差异,4、6月优势度指数高,主要是优势种马口鱼、月斑长臀鲃造成。4、5月鱼类组成相似性最高。最低水位对鱼类数量影响最大,其次是平均流速和平均水温;最高水温对鱼类体重影响最大,其次是总磷和溶解氧。人工神经网络下模拟值与实测值相关性高,具较好的适用性。     

The fate of organic matter derived from small-scale fish cage aquaculture in coastal waters of Sulawesi and Sumatra, Indonesia

To determine the fate of organic matter derived from fish cage aquaculture, carbon and nutrient cycling processes in waters and sediments, and water circulation, were examined at two fish cage farms of different size and utilizing different food types, on Sulawesi and Sumatra islands, Indonesia. Mass balance models of C, N and P were constructed to assess the pathways of waste utilization and dispersal. At the smaller farm in Sulawesi (64.5 m² cage area; 3 t annual net production) using pelleted food, there was proportionally less waste (≈ 40% of total C input) than at the larger Sumatran farm (2432 m² cage area; 9 t annual net production) using trash fish (≈ 70% of total C input) as food. At the small farm, the mass balance and hydrographic models indicated a maximum dispersal area of 1180 m², equivalent to 18 times the farm area. Within this area, 30% of total organic matter input (farm waste + fixed phytoplankton carbon) was buried in sediments with 30% mineralized in the water-column and 40% mineralized in the seabed. At the larger Sumatran farm, the models indicated a maximum dispersal area of 29  220 m², roughly 12 times the farm area. Within this area, 30% of total organic matter input (farm waste + natural pelagic input) was buried in sediments with 50% mineralized in the water-column and 20% mineralized on the seabed. There was some evidence of benthic enrichment at both farms, mostly as enhanced dissolved nutrient release, but sulfate reduction accounted for < 25% of total C flux, and denitrification/ammonium oxidation accounted for only 4–17% of N lost from sediments. There was no clear evidence of impact with distance from the cages at either farm. Phytoplankton gross primary production accounted for 60–77% of the total organic input to the receiving environment, suggesting that the relative importance of fish cage wastes must be assessed against natural inputs of organic matter.     

Environmental effects of a marine fish farm of gilthead seabream (Sparus aurata) in the NW Mediterranean Sea on water column and sediment

This study examined the effects of organic enrichment on water column, sediments and macrofauna caused by a fish farm in the Mediterranean Sea. Samples were collected on four sampling campaigns over a one‐year cycle. Significant differences were found in the water column in dissolved oxygen, dissolved inorganic nitrogen, phosphate and total phosphorus concentrations between the fish farm and the control. The increase in the dissolved inorganic nitrogen and phosphate concentrations at the fish farm modified the stoichiometric ratios between nutrients, with silicate acting as limiting nutrient at the fish farm 11% more than at the control. Nevertheless, chlorophyll a concentration in the water column was higher at the control station, probably due to the fouling of the underwater fish farm structures. Significant differences were found in sediment concentrations of organic matter, total phosphorus and redox potential between the fish farm and the control. The Canonical Correlation Analysis indicated that organic matter, total phosphorus, redox potential and% of gravels accounted for 68.9% of the total variance in the species data. Changes were observed in macrofauna, with a decrease in number of species and up to a nine‐fold increase in abundance with respect to the control.     

Impact of fish and pearl farming on the benthic environments in Gokasho Bay: Evaluation from seasonal fluctuations of the macrobenthos

ABSTRACT: In order to clarify the influence of mariculture on the benthic fauna, samples of the macrobenthos were collected from Gokasho Bay, where intensive fish culture and pearl oyster culture have been carried out. Monthly samples collected from the fish farm and pearl farm sites during June 1995 to July 1996 revealed that the community structure of the two sites showed distinct differences with seasonal fluctuations. At the fish farm site, azoic conditions were found from July to November; after December, the diversity increased markedly through successive recruitments of small-sized species such as the polychaetes Capitella sp. and Pseudopolydora paucibranchiata , and the amphipods Aoroides spp.; macrofaunal density, biomass and species richness peaked from March to April. At the pearl farm site, a higher diversity, including larger-sized species, and no clear seasonal fluctuations in abundance was found, and the community structure was similar to that at the control site. These results show the large impact by fish farming on the macrofauna, whereas pearl farming causes less effect on the benthic fauna. It is suggested that the difference in the level of organic input between the two sites results in the differences in the dissolved oxygen content of the bottom water, sulfide content of the sediments and, subsequently, the macrobenthic assemblages.     

Monitoring of oxygen fluctuations in seabass cages (Dicentrarchus labrax L.) in a commercial fish farm in Greece

Dissolved oxygen and temperature were monitored in cages stocked seabass at a commercial fish farm in Greece during summer and autumn. During the first part of the study, October–November 2012, current velocity monitoring outside the cages supported the sampling program. The latter sampling took place during May–July 2014. Including both periods, temperature fluctuated within the range 18–26°C while the current velocity, dominated by the tidal flow, varied from 0 to 28 cm/s in autumn. During sampling, seabass of 400–550 g individual weight was stocked at a density of 10–15 kg/m³. Within the cages, dissolved oxygen (DO) saturation decreased by 10% to 50% compared with outside levels. In‐cage oxygen concentrations seemed to be affected by current speed, temperature and diurnal fluctuations due to the fish stock's activity and the day‐night rhythm of algae. Hypoxia within the range 40%–70% of oxygen saturation was shown in several cases, despite the fact that the feeding intensity was quite low in the farm. The diurnal pattern of DO saturation showed that minimum levels coincided with feeding of the fish, while photosynthesis played a minor role in this case. This level of DO saturation although does not result in any mortalities may have other severe implications, especially at high temperature, such as lower feed utilization, increased metabolic expenses due to osmo‐respiratory compromise, increased stress level, lower disease resistance and diminished fish welfare.     

Effect of fish farming on the water column nutrient concentration in a semi-enclosed gulf of the Eastern Mediterranean

The spatial and seasonal impact of fish farming on the water column of two fish farms in the Eastern Mediterranean was investigated, between July 2004 and April 2005. In the area of each fish farm, three stations were sampled. One was located at the centre of the fish farm, the other at a distance of 50 m from the centre and the last one at a distance of 300 m from the fish farm centre. At each sampling station, water samples were collected at the surface, at 5 m and at every further 10‐m depth from the surface to the bottom, for nutrient analysis (ammonium, nitrite, nitrate, phosphate, silicate). Statistical analysis showed significant differences between seasons for all nutrients, with the exception of nitrite in one of the farms. Furthermore, ammonium, nitrite, phosphate and silicate values showed significant differences among sampling stations. The maximum concentrations of the above nutrients (1.64, 0.10, 2.57, 0.28 and 4.89 μM respectively) were recorded at the sampling stations located at the centre of each fish farm and they were gradually reduced with increasing distance from the cages. The concentrations of nutrients did not appear to exceed permitted levels for the appearance of eutrophication. The maximum concentrations were considerably lower than those observed previously in the study area.     

Production of the Endangered Rio Grande Silvery Minnow,Hybognathus amarus,in the Conservation Rearing Facility at the Los Lunas Silvery Minnow Refugium

This article describes the initial season‐long yield trial of raising the endangered Rio Grande silvery minnow, Hybognathus amarus, in the conservation rearing facility at the Los Lunas Silvery Minnow Refugium. Ten thousand fish (90,900/ha) were stocked on June 22, 2010. Production was based on a total of 653 mL (5.936 L/ha) of 11‐37‐0 N‐P‐K and 5.5 kg (50 kg/ha) of alfalfa pellets. Fish were harvested in October; almost all were harvested 18–27 October. At stocking, fish averaged 21.7 mm total length and mean weight was 0.10 g. At harvest, fish averaged 48.98 mm and 1.12 g. Fish were sampled monthly, and increased lengths and weights through the study were significant (P = 0.05). Five thousand eight hundred ninety‐two fish were harvested (58.92% survival). Yield was 59.99 kg/ha. Temperature, dissolved oxygen (DO), pH, un‐ionized ammonia, nitrite, turbidity, alkalinity, and chloride were measured at seven sites throughout the outdoor refugium. Secchi disc visibility was measured in the stream and in the ponds. Only two variables (DO and pH) went outside permitted values, but were easily corrected. Harvest was difficult due to the many different naturalized areas consisting of varying depths, channel widths, and substrates.