Effect of dietary protein level on the reproductive performance of Nile tilapia, Oreochromis niloticus (L.)

The effects of five dietary protein levels (25%, 30%, 35%, 40% and 45%) on the individual spawning frequency and the egg production of 135 tagged female Nile tilapia, Oreochromis niloticus (L.), were studied from 8 May to 19 November 1996 in outdoor concrete tanks. Virtually identical spawning patterns were found in all treatments, but there was a great deal of variation in the frequency of spawning and egg production. Overall, individual spawning frequency varied from one to 14 and individual egg production from 31 to 2828 eggs per spawning. The average number of spawnings and average number of eggs per spawning for fish receiving dietary protein levels of 25%, 30%, 35%, 40% and 45% were 8.0 ±1.6, 8.4 ± 2.2, 8.5 ± 2.7, 8.4 ± 2.5 and 9.4 ± 2.1 spawnings, and 1167 ± 305, 1082 ± 410, 1288 ± 324, 1145 ± 389 and 1328 ± 311 eggs per spawning, respectively. Fish receiving 45% dietary protein spawned more frequently than fish receiving 25% dietary protein. The total number of eggs produced per female was significantly higher for females fed 45% protein feed than females receiving 25% and 30% protein feeds. No definite trend was found in the number of eggs produced per spawning and the number of eggs produced per gram in females fed at different protein levels. Based on weekly checking, the time interval between spawnings varied from 7 to 77 days, and mean spawning intervals ranged from 15.8 to 17.1 days. Sixty per cent of females spawned after an interval 14 days, 15% after 21 days, 13.6% after 7 days, 7.2% after 28 days, 1.8% after 35 days and 1.0% after 42 days, and the time interval was 49-77 days for the rest of the females (1.5%). In all treatments, maximum spawning activity was recorded from May to August, and thereafter, it gradually decreased and no spawning females were found in November.     

Spawning of injured compared to uninjured female Atlantic salmon, Salmo salar L.

Abstract. Observations of spawning by uninjured and injured Atlantic salmon, Salmo salar L., indicated that uninjured fish usually spawned in the outlets, or inlets, to pools and on coarse bottom sediments, whereas injured females spawned in different places. Frequently, the spawning sites lay in very shallow water with a slow current and on a bed of sand or fine gravel. Subsequent excavation of the spawning redds revealed that about 28% of the eggs laid by uninjured females were recovered, compared with only about 8% of those laid by injured females. This difference was significant (P < 0·01).     

Substrate choice of territorial male Topeka shiners (Notropis topeka) in the absence of sunfish (Lepomis sp.)

Abstract –  Topeka shiners ( Notropis topeka ), an endangered minnow species, typically spawn on or around breeding Lepomis sunfish (Centrarchidae) nests. Why spawning Topeka shiners are attracted to these nests is unclear, but having the nesting sunfish provide shiner eggs with improved aeration, a lessening of siltation, and protection from egg predators are possibilities. We tested the substrate utilisation of Topeka shiners in outdoor tanks in the absence of sunfish to determine the shiner's fundamental choice. Shiners were provided with substrate patches of cleaned sand, small gravel, large gravel, and small cobble, and the bare floor of the tank. The substrate above which a male shiner established his territory was used as evidence of choice. A statistically significant choice for sand substrates was demonstrated. This fundamental choice might influence which sunfish nests Topeka shiners use, given that nest substrate characteristics differ both between sunfish species and within species by spawning site location.     

An hypothesis on the light requirements for spawning penaeid shrimp,with emphasis on Penaeus setiferus

Using standard equations, we have concluded that the light intensities which have been used by investigators attempting to induce maturation and spawning are up to 4000 times higher than would occur over the spawning grounds of Penaeus setiferus, a species for which successful controlled spawning has yet to be achieved. We recommend that future attempts at captive maturation and spawning with that species be conducted at light levels of no more than 12 μW cm^?2 and that the intensity at which other species of shrimp are matured and spawned be examined relative to natural light levels on their spawning grounds. It is further recommended that the need for light of blue or green color be evaluated for its role as a promotor of maturation and spawning. The intent of these modifications in current spawning procedures is to eliminate the need for eyestalk ablation in captively spawned penaeid shrimp.     

Does sand content in spawning substrate result in early larval emergence? Evidence from a lithophilic cyprinid fish

The spawning success of lithophilic salmonids is strongly influenced by the fine sediment content (“fines”) of spawning substrates, yet knowledge on the impacts of fines on the spawning of non‐salmonid lithophiles remains limited, despite their ecological and socio‐economic importance in European rivers. Consequently, the aim here was to use an ex‐situ experiment to investigate the impact of sand content on egg survival and timing of larval emergence of the surface‐spawning cyprinid European barbel Barbus barbus. Thirty incubator boxes within a recirculating system were filled with one of five experimental sediment mixtures (0%–40% sand by mass) that each contained 300 fertilised eggs at a depth of 50 mm. Emerged, free‐swimming larvae were captured and counted daily to assess grain‐size effects on larval survival and emergence. Specifically, total proportion of emerged larvae, cumulative daily proportion of emerged larvae and time required to reach 50% emergence were measured during the study. Whilst the proportion of sand in the sediments did not have a significant impact on egg‐to‐emergence survival (mean survival per treatment 75%–79%), it significantly affected the timing of larval emergence to the water column; early emergence was detected in treatments with elevated sand content (on average, 50% emergence after 12–13 days versus 19 days in the control). Similar to findings from salmonid studies, these results suggest high sand content in spawning gravels can influence timing of larval emergence and potentially cyprinid lithophilic fish survival.     

Notes on hatchery spawning methods for bigmouth sleeper Gobiomorus dormitor

The bigmouth sleeper Gobiomorus dormitor, a popular sport fish within its native range, offers a management alternative to exotic species currently managed for recreational fishing. Hatchery production and stocking are needed to create reservoir sport fisheries because this species usually requires access to marine environments for recruitment. Bigmouth sleepers have not been spawned previously in a hatchery, and hence we used natural, artificial and semi‐natural spawning techniques. No egg deposition or propagation resulted from natural pond spawning. Artificial spawning techniques using Ovaprim^® and Chorulon^® injections followed by hand stripping were more successful. Semi‐natural (hormone injections plus volitional spawning) spawning trials using Ovaprim^® and Chorulon^® displayed the greatest potential, and three consecutive evening injections (1.0 mL kg^?1) of Chorulon^® appeared most conducive. High‐fecundity spawning was achieved by injecting bigmouth sleeper pairs and allowing volitional spawning in aquaria with spawning cavities. Initial success in 2007–2008 was isolated to wild‐caught fish, but captive broodstock were spawned using these techniques in 2009. Eggs hatched in <20 h at 23–24 °C. The resulting larvae, 1.0–1.5 mm in length, displayed large yolk sacs, unpigmented eyes and no apparent mouth. These hatchery propagation efforts suggest that hormone‐induced semi‐natural spawning has the greatest potential for bigmouth sleeper propagation.     

Volitional Spawning of Black Sea Bass Centropristis striata Induced with Pelleted Luteinizing Hormone Releasing Hormone-Analogue

The black sea bass is a high‐value marine serranid and is a prime candidate for intensive cultivation. Reliable methods for controlled spawning are needed to accelerate the development of hatchery technologies that result in mass production of healthy juveniles. During 1998–2001, spawning studies were conducted at The University of North Carolina at Wilmington (UNCW) and at the South Carolina Department of Natural Resources (SCDNR), Charleston, using pelleted luteinizing hormone releasing hormone analogue (LHRH‐a). From April through July 2001, 28 vitellogenic‐stage females, with mean oocyte diameters (MOD) ranging from 277–448 μm, were implanted with a 95% cholesterol‐5% cellulose pellet containing LHRH‐a (‐50 μg/kg body wt) at UNCW. In 10 individual spawning trials, females with MOD of 305–448 μm and maximum oocyte diameter × 475 μm spawned volitionally beginning 2–3 d post‐implantation (PI) and continued spawning over an average of 1.9 d (range = 1–4 d). Individual females released a mean total of 149,000 eggs (117,000 eggs/kg) with a mean buoyancy rate of 40.5% (floaters). Fertilization and hatching rates were 98% and 27.2% of floaters, respectively, yielding 14,600 yolksac larvae/female (12,600 yolksac larvae/kg body wt), and overall egg viability averaged 8.9%. In eight group spawning trials (2–3 females/group), average performance of females, including fecundity (103,800 eggs/female; 105,500 eggs/kg body wt), buoyancy rate (42.5%), fertilization and hatching rates (97.7% and 24.3% of floaters), numbers of yolksac larvae produced (10,900 yolksac larvae/female; 10,100 yolksac larvae/kg body wt), and overall egg viability (10.6%) was comparable to what was seen in individual spawning trials. From 1998–2000, a total of 58 vitellogenic stage (70% of oocytes 500 pm) females were implanted with pelleted LHRH‐a (‐50 μg/kg body wt) in nine group spawning trials (2–19 females/group) at SCDNR. Volitional spawning typically began 18–42 h PI and recurred every 1–3 d for an average duration of 9 d. Female groups released a mean of 560,000 eggs (84,000/female; 132,000/kg body wt) over the spawning period, with mean buoyancy rate of 25.7% floaters. Fertilization and hatching rates were 17.7% and 11.6 % of floaters, respectively, yielding 4,300 yolksac larvae/female (4,600 yolksac larvae/kg body wt). Overall egg viability was 2.9%. Captive wild‐caught black sea bass were induced to undergo repetitive volitional spawning by implantation of pelleted‐LHRH‐a, consistent with a multiple clutch group synchronous pattern of ovarian development. Group spawning appears to be a practical way to compensate for variable fecundity and egg viability of individual females. Research is needed to identify optimum hormone treatments and eligibility requirements.     

The use of brushwood bundles as fish spawning media

Salford Quays is a redeveloped freshwater dockland, which initially constituted part of the grossly polluted Manchester Docks, Manchester, UK. Such water bodies are characterized by a lack of suitable spawning sites and littoral refuges, and this will act to reduce fish recruitment. To redress this, a variety of artificial spawning substrates were introduced to these waters. Spawning structures were made from bundles of different types of thin brushwood suspended from the dock walls. Roach, Rutilus rutilus (L.), spawned on bundles of willow, Salix alba (L.), and spruce, Pilea abies (L.), branches, whilst perch, Perca fluviatilis L., spawned on bundles of willow, sycamore, Acer pseudoplatanus (L.), spruce and plastic netting. Unused bundles were made up of lime, Tilia platyphyloss (Scop.), pear willow, Pyrus salicitolia (Pall.), and laurel, Laurus nobilis (L.). Perch spawning began around 20 May and showed a preference for open structures (between one and three ribbons per bundle). Roach spawning began about 10 days after perch and showed a preference for dense bundles of spruce (geometric mean egg density 1.5 cm^{? 2} spruce). The use of such structures in fisheries management is discussed.     

The effect of short-term starvation on ovarian development and egg viability in rainbow trout (Salmo gairdneri)

Adult female rainbow trout (Salmo gairdneri) were fed a commercial trout production diet until approximately 40 days prior to spawning at which time the fish were divided in two groups. One group continued to be fed while the other group was starved until spawning. Egg size, egg number, ovary weight, and egg proximate composition were examined periodically starting 5 months before spawning. Muscle tissues of the fish were sampled at spawning to measure somatic depletion of proximate consituents in the two groups. Egg hatchability was determined by incubating test lots from each spawning female. No significant differences (P > 0.05) were found in egg hatchability between the fed and starved groups. Changes in proximate composition were observed in the eggs during the months prior to spawning, but no differences were detected between the eggs of the starved and the fed groups. Short-term starvation did not significantly alter the proximate composition of muscle tissue of the spawned female trout.     

Modelling the effect of buoyancy on the transport of anchovy (Engraulis capensis) eggs from spawning to nursery grounds in the southern Benguela: an IBM approach

An individual‐based model (IBM) was used to investigate the effects of physical and biological variables on the transport via a jet current of anchovy (Engraulis capensis) eggs from spawning to the nursery grounds in the southern Benguela ecosystem. As transport of eggs and early larvae is considered to be one of the major factors impacting on anchovy recruitment success, this approach may be useful to understand further the recruitment variability in this economically and ecologically important species. By coupling the IBM to a 3D hydrodynamic model of the region called Plume, and by varying parameters such as the spatial and temporal location of spawning, particle buoyancy, and the depth range over which particles were released, we could assess the influences of these parameters on transport success. A sensitivity analysis using a General Linear Model identified the primary determinants of transport success in the various experimental simulations, and model outputs were examined and compared with patterns observed in field studies. Model outputs compared well with observed patterns of vertical and horizontal egg distribution. Particle buoyancy and area of particle release were the major single determinants of transport success, with an egg density of 1.025 g cm^?3 maximizing average particle transport success and the western Agulhas Bank being the most successful spawning area. This IBM may be useful as a generic prototype for other upwelling ecosystems.     

Reproductive performance in induced and spontaneous spawning of the mangrove red snapper, Lutjanus argentimaculatus: a potential candidate species for sustainable aquaculture

A reliable breeding technique was developed for the mangrove red snapper, Lutjanus argentimaculatus (Forsskal 1775), to help sustain the aquaculture of this immensely popular species in Southeast Asia. Using standardized indices of female maturity (based on mean oocyte diameter of ≥0.40 mm), time of injection (1000–1130) and sex ratio (one female to two males), a single injection of 100 μg kg^?1 luteinizing hormone‐releasing hormone analogue (LHRHa) (n=16 fish), but not 50 μg kg^?1 (n=five fish), successfully induced egg (62.5% success rate) and larval (43.8%) production. Human chorionic gonadotropin (hCG) at 500 IU kg^?1 (n=five fish) also failed to induce spawning, but doses of 1000 (n=22 fish) and 1500 IU kg^?1 (n=15 fish) gave spawning (77.3% and 80.0% respectively) and hatching success rates (72.7% and 60.0% respectively) that were not significantly different from those of 100 μg kg^?1 LHRHa. No spawning was observed in saline‐injected controls (n=seven fish). While mean spawning latency, egg diameter, egg production per spawn, percent egg viability, hatching rate, percent of normal larvae and cumulative survival of eggs to normal larvae did not differ significantly among the effective hormones and doses, 1000 IU kg^?1 hCG had a higher percentage (76.5%) of total spawns with egg production per spawn in excess of one million than those of 1500 IU kg^?1 hCG (50.0%) and 100 μg kg^?1 LHRHa (40.0%). Mangrove red snapper spontaneously spawned from March–April to November–December with a peak of egg collection and spawning in May–June. Egg collection per spawn ranged from 0.05 to 6.35 million. Spontaneous spawning of mangrove red snapper exhibited lunar periodicity with spawns mostly occurring 3 days before or after the last quarter and new moon phases and occurred consistently between 02:00 and 04:00 hours. High fecundity and good egg quality, coupled with the ability to respond to induce spawning or natural spawning in captivity, provide a sound basis for improving the sustainability of red snapper aquaculture in Southeast Asia.     

The impact of repeat spawning of males on effective number of breeders in hatchery operations

In conservation hatcheries, typically a great emphasis is placed on maximizing the effective number of breeders through spawning an appropriate number of spawners, spawning equal numbers of males and females when possible, and by mating either in a single-pair or factorial fashion. A commonly encountered problem, especially in small operations with anadromous salmonids, is a shortage of males at some point during the season, so that some males need to be spawned multiple times. This has an impact on the genetically effective number of breeders, and the commonly used equations for effective number are not applicable. In this paper I derive a relatively simple equation for effective number of breeders when some males are multiply spawned but reproductive contribution within spawning classes are equal: , where i is the number of times a male is spawned, N_i the number of males spawned i times, and μ_t the mean gametic contribution. I also derive an equation that allows relaxation of the assumption of equal contribution within classes. I then develop a number of simple and accurate approximations for the effective number of breeders. The equations can be applied to any situation in which there are discrete spawning classes in which the average reproductive contribution of any one class can be expressed as a multiple of that of another class.     

Characteristics of a Pacific herring Clupea pallasii spawning bed off Minedomari, Hokkaido, Japan

ABSTRACT:   The spawning bed selection of herring Clupea pallasii off Minedomari, Atsuta, on the west coast of Hokkaido, Japan, is discussed in relation to the topography of the rocky shore and wave conditions during the spawning season. From 1998 to 2003, herring have spawned their eggs mainly on the leaves of the seagrass Phyllospadix iwatensis Makino in almost the same site on the rocky shore off Minedomari in the Atsuta area. The site is connected to a valley-like feature offshore. Wave conditions were surveyed at Minedomari during the spawning season in 2000 and the wave height was estimated from 1998 to 2003, except for in 2000, using the correlation of wave height between Minedomari and Ishikari Bay New Port, approximately 18 km south-west of Minedomari. Herring spawned under calm conditions, during which the wave height was approximately 0.5 m off Atusta and Aoshima and was 0.18–1.28 m off Minedomari. The distribution of water particle velocity on the sea bottom surface as a result of ocean waves off the Minedomari area, which was estimated based on the wave height and the topography of the coast, suggested herring could swim easily into the shallower area along the valley-like feature off Minedomari. Therefore, topographical features are thought to be one of the reasons why herring have used Minedomari as a spawning bed. Additionally, seepage of freshwater from the bottom, which was observed in this area, could also be the reason why herring spawn in Minedomari repeatedly.     

春季钓鱼岛海域竹鱼产卵群体生物学特征的研究

利用2005年3月在钓鱼岛海域捕获的竹鱼产卵群体样品测定数据,对其主要生物学特征、主要产卵期和繁殖力特征进行了研究。结果表明,钓鱼岛海域是春季东海南部竹鱼的主要产卵场,主要产卵期为3月中下旬。根据叉长和体重的频率分布图,可以看出该产卵群体主要有3个叉长优势组,其中以200～220mm和230～240mm叉长组为主,260～270mm叉长组个体极少;体重的组成特征与叉长组成基本一致。由于所取样品处于产卵后期,因此条件生长因子相对较小。个体绝对生殖力在12264～37629粒/尾,个体平均绝对生殖力为27844±10179粒/尾;单位长度生殖力范围为50～157粒/mm,平均值为121±42粒/mm;单位纯体重生殖力为82～238粒/g,平均值为202±68粒/g。     

An experiment in rearing larval Siganus vermiculatus (Valenciennes) and some observations on its spawning cycle

Siganus vermiculatus spawned in captivity on three occasions, and limited numbers of newly hatched larvae were stocked in an 80-m³ outdoor concrete tank and a 2000-m² fish pond in Fiji. Survival through the larval stage was 9% in the tank, in spite of high temperatures and relatively low food densities. No larvae survived in the pond.Data collected on the appearance of fry, spawning, and the gonadal state of adults suggest that S. vermiculatus in Fiji spawns monthly on or around the first lunar quarter during its spawning season.Possible ways to solve problems encountered in this experiment are discussed.     

Characterization and comparison of variations in reproductive performance of Chitralada strain Nile tilapia, Oreochromis niloticus (L.)

In an attempt to better understand and characterize the variability in the female reproduction of individual Thai‐Chitralada strains of Nile tilapia, Oreochromis niloticus (L.), tagged mature females (n=68) from a single population were monitored in a hapa‐in‐pond system over a 12‐month experimental period. Spawn female⁻¹, eggs female⁻¹ day⁻¹, eggs kg female⁻¹ day⁻¹, day spawn⁻¹ and weight (g) at first spawning of individual females were determined from the regular weekly sampling of weight (g) and eggs per spawn. For analysis, the females were grouped into two, high spawning (HSF) and low spawning frequency (LSF) classes based on their spawning frequency (SF) record. Moreover, nested under these two classes were two groups each based on growth rate, i.e., high frequency – large size (HL), high frequency – small size (HS), low frequency – large size (LL) and low frequency – small size (LS). There was no difference in eggs spawn⁻¹ among all females. The HSF group produced 68% and 361% more eggs female⁻¹ day⁻¹ than the population mean and LSF group respectively. Eggs female⁻¹ day⁻¹ and spawn female⁻¹ remained high in the HSF group and low in the LSF group throughout the 12‐month experimental period. This suggests that individual female spawning activity is consistent within a population in a common environment. The inter‐spawn interval increased with age in all four groups, and day spawn⁻¹ was shorter by 130% in HSF females compared with day spawn⁻¹ in LSF. The HSF group also spawned more successively (≥3), while the LSF group of females had fewer successive spawns (≤2). Body weight (g) had no influence on the number of eggs produced. The study indicates that separating frequently spawning females could be used as an important strategy to improve commercial seed production of Nile tilapia.     

Reproductive development, GnRHa-induced spawning and egg quality of wild meagre (Argyrosomus regius) acclimatised to captivity

The objective of the study was to acclimatise wild-caught meagre (Argyrosomus regius) to captivity to produce viable eggs for aquaculture production. Twelve meagre (3 males and 9 females, mean weight?=?20?±?7?kg) were caught and transported to a land-based facility on 26 October 2006. During, March to June 2007, all three males were spermiating and five of the nine females were in vitellogenesis with mean maximum oocyte diameter ≥550?μm. No spontaneous spawning was observed. Two hormone treatments, either a single injection of gonadotropin-releasing hormone agonist (GnRHa, 20?μg?kg(-1) for females and 10?μg?kg(-1) for males) or a slow-release implant loaded with the same GnRHa (50?μg?kg(-1) for females and 25?μg?kg(-1) for males), were used to induce spawning on three different dates on 26 March 2007, 4 May 2007 and 18 April 2008. From each spawning event, the following parameters were determined: fecundity, number of floating eggs, egg size, fertilisation and hatching success, unfed larval survival, and proximal composition and fatty acid profile of the eggs. In 2007, two females that were injected on 26 March and 4 May spawned a total of 5 times producing 9,019,300 floating eggs and a relative fecundity of 198,200 eggs?kg(-1) and two different females that were implanted on the same dates spawned 14 times producing 12,430,000 floating eggs and a relative fecundity of 276,200 eggs?kg(-1). In 2008, a pair that was implanted spawned five times producing a total of 10,211,900 floating eggs and a relative fecundity of 527,380 eggs?kg(-1). The latency period was 48-72?h. Parameters were compared between hormone treatments, date of hormone induction and parents determined by microsatellites. Percentage hatch and egg size were 70?±?0.3% and 0.99?±?0.02?mm, respectively, for GnRHa-implanted fish and were significantly higher (P?相似文献   

Characteristics and rehabilitation of the spawning habitats of the sea trout, Salmo trutta, in Gotland (Sweden)

Characteristics of the natural spawning habitat of sea trout, Salmo trutta L., were studied in Själsöån, a small stream of Gotland, Sweden, from 1992 to 1999. Each year, trout spawned on 17 ± 7 different areas (156 places ha^?1). Most of the spawning grounds were used every year. Overcutting was evident for at least 60% of the spawning grounds. Fish spawned on a gravel of 19 ± 7 mm in diameter. From 1978 to 1992, 242 artificial spawning grounds were constructed by the Gotland Sport Fishermen Association in four Gotland streams. A sediment trap was dug upstream to the spawning grounds. The artificial spawning ground comprised of a downstream V‐shape stream deflector of large stones with a log weir at the narrowest point of the deflector. Upstream of the dam, 15–60 mm diameter gravel was deposited to constitute the spawning ground substratum. To keep the installation efficient, maintenance is needed every year before the spawning season.     

Induced winter spawning and culture of larvae of the blue crab, Callinectes sapidus rathbun

Female blue crabs were induced to produce eggs out of their normal spawning season. One group of crabs, held in the laboratory at 19° C, was fed every 7 days; another group, held at 15° C, was offered food at the same interval. Photoperiod simulated ambient winter conditions in both groups. Of ten crabs held at 19° C, two produced egg masses and one died when spawning was about to commence. Among those crabs not producing egg masses during the experiment, ovarian development at 19° C proceeded further than among those held at 15° C.Survivorship of larvae from induced eggs raised on a rotifer diet was comparable with that for naturally spawned larvae through the first 28 days of development.Zoeae survived well to metamorphosis when fed a diet of rotifers during the first two stages, followed by Artemia salina nauplii. However, only six zoeal stages were present instead of the usual seven. Possible explanations for this observation include genetically controlled variation, variation due to origin of eggs (induced), or effect of diet.Survivorship and growth were not adversely affected when synthetic sea water was used as the culture medium.     

Inhibiting fungus on largemouth bass eggs with copper sulfate and its toxicity to fry and juveniles

This study determined the effectiveness of copper sulfate (CuSO₄) to inhibit fungal growth (caused by Saprolegnia spp.) on largemouth bass (LMB) eggs spawned on/in fiber mats in very high-alkalinity/-hardness waters; experiments also determined the toxicity of CuSO₄ to LMB fry and juveniles. An untreated control and three CuSO₄ concentrations (10, 20, and 40 mg/L) were tested under a flow-through scenario in the effectiveness experiment. Eggs were treated daily until hatching began. Fungal load at the time of hatch had a total area > 3.0 cm² in the untreated controls, total area 1.0 to <2.0 cm² in the 10 and 20 mg/L CuSO₄ treatments, and total area > 1.0 cm² in the 40 mg/L CuSO₄ treatments. Fungus samples were identified as Saprolegnia australis. The 24-hr median lethal concentration (LC50) values on the LMB yolk-sac and swim-up fry were 32.0 and 4.6 mg/L CuSO₄, respectively; the No Observed Effect Concentrations (NOEC) were 16.0 and 0.125 mg/L CuSO₄, respectively. Juvenile LMB were extremely tolerant to CuSO₄, and their 24-hr LC50 value was 185.5 mg/L; the NOEC was 64 mg/L. This study indicates that CuSO₄ can be an important resource for hatcheries to control egg fungus, especially in high-alkalinity/-hardness waters.