Pharmacokinetics and tissue distribution of oxytetracycline in carp, Cyprinus carpio L., following different routes of administration

Abstract. The objective of this pharmacokinetic study was to investigate absorption, distribution, elimination and bioavailability of oxytetracycline (OTC) in carp, Cyprinus carpio L ., after different routes of administration, OTC was administered intravenously (i.v.), intramuscularly (i.m.) and orally at 60 mg/kg body weight. OTC levels were determined in plasma and several tissues. Analysis of the plasma drug concentration-time curves following i.v. OTC injection revealed three distinct phases. A three-compartment open model was used to derive pharmacokinetic parameters. Compared to mammals, a very extended final elimination half-life was observed (139.8±38.1 h). Following i.m. OTC administration, C_max was 56.8±10.9μg OTC/ml at 14 h post-injection. The Vd area was 2.1 ± 0.66 1/kg. Extreme differences were observed with respect to bioavailability following i.m. and oral administration; approximately 80 and 0.6%, respectively. Following i.m. injection tissue OTC determinations revealed that the drug was accumulating in pronephros, bone tissue and scales. After 21 days the OTC concentrations were 2.9±0.8, 5.2±0.3 and 4.7±3.1 μg/ ml, respectively. In tissue samples from the dorsal region (muscle), including the injection site, OTC could not be demonstrated at that time. The pharmacokinetic data are discussed in relation to the susceptibility of the immune system of fish for modulation.     

Effect of dietary protein levels on growth of Penaeus stylirostris juveniles

The shrimp Penaeus stylirostris is currently produced on a commercial scale in Tahiti and New Caledonia. Both super-intensive (80 animals m⁻²) and semi intensive (25 m⁻²) systems are promoted. Locally produced commercial feed contains 380–400 g kg⁻¹ crude protein (CP) without special consideration for environmental impact. The need for a 'low pollution' diet implies reconsideration of the optimum dietary protein level for this species. Under experimental conditions, six isoenergetic practical diets ranging from 270 g kg⁻¹ to 440 g kg⁻¹ CP were formulated and fed to satiation for 30 days to juvenile P. stylirostris ; average growth rates were between 5.5 and 7.5 g per month with survival rates > 90%.
The lowest protein levels 270–310 g kg⁻¹, gave significantly ( P < 0.05) poorer growth (5.5 g per 30 days) than was observed with 330–430 g kg⁻¹ CP; 330 g kg⁻¹ CP may be recommended, and as it is lower than levels in diets used currently, there is a possibility of reducing nitrogenous waste. In addition to growth response, protein efficiency ratio, protein productive value and food conversion (feed/gain) all supported a recommended dietary protein level of 330 g kg⁻¹. Future prospects for practical feeds with even lower CP levels are considered.     

Perception of light intensity by Haliotis discus discus based on locomotor activity patterns

ABSTRACT:   An apparatus to measure the locomotor activity of aquatic benthic organisms at variable low light levels was developed and the diurnal behavioral pattern of the abalone Haliotis discus discus was measured at various low light intensities. During the experiment, abalone were exposed to 12 h light–dark cycles of complete darkness, 0 µmol/m²/s throughout the 12 h dark cycle and, during periods I (days 1–8) and III (days 19–26), the 12 h light cycles were set at 10 µmol/m²/s. During period II (days 10–17), abalone were exposed to a light level during the 12 h light cycles of 1 × 10⁻⁵, 1 × 10⁻⁶, 1 × 10⁻⁷ or 1 × 10⁻⁸ µmol/m²/s and the changes in locomotor activity assessed. At daytime levels of 1 × 10⁻⁵ µmol/m²/s, typical behavioral patterns were observed of high locomotory activity during the night-time cycle. However, at lower light intensities, the distinction between day and night activity patterns became less clear and, at intensities lower than 1 × 10⁻⁷ µmol/m²/s, the difference between activity during the light and dark cycles became negligible. Based on this, we conclude that the threshold of light level perception in relation to locomotor activity is approximately 1 × 10⁻⁷ µmol/m²/s. The significance of these results in relation to the entrainment of behavior in abalone is discussed.     

Effect of synthetic GnRH analogues and dopamine antagonists on the maturation of Pacific mullet, Mugil so-iuy Bas.

Abstract. The effect of two GnRH-As – des Gly¹⁰ (D-Ala)⁶ LHRH and des Gly¹⁰ (D-Tle)⁶ GnRH in total doses 10–249mu;g/kg – and four neuroleptics – pimozide, sulpiride, metoclopramide and isofloxythepin in total doses 1–50mg/kg - and environmental temperatures on the development of final stages of Pacific mullet oogenesis was investigated. The best technique of those used by us for spawning stimulation of Pacific mullet, Mugil so-iuy Bas., females is shown to be administration of neuroleptics in doses of l-8mg/kg with posterior injections on GnRH-A in doses of 25 and 50mu; g/kg applied 4 and 28h respectively after the neuroleptic injection. At water temperatures below 17°C, ovulation does not occur unless the optimal stimulation is applied.     

Anaesthetic efficacy and physiological responses to clove oil-anaesthetized kelp grouper Epinephelus bruneus

The efficacy of clove oil as an anaesthetic and at producing a physiological response (plasma cortisol and glucose) was evaluated in the kelp grouper, Epinephelus bruneus . To acquire complete anaesthesia in less than 3 min and recovery in <10 min, three doses of clove oil were tested at 18, 22 and 26 °C. Although higher anaesthetic doses resulted in shorter induction times and longer recovery times, and a lower temperature resulted in longer anaesthesia induction and slower recovery, we found the optimal dose and administering temperature of clove oil to be 250–300 mg L⁻¹ at water temperature of 18 °C, 150–200 mg L⁻¹ at water temperature of 22 °C and 50–100 mg L⁻¹ at water temperature of 26 °C respectively. Following the administration of 150 mg L⁻¹ of clove oil at 22 °C, the plasma cortisol level was highest (4.24 ± 1.571 μg dL⁻¹) after 12 h and the plasma glucose was highest (92.7 ± 9.61 mg dL⁻¹) after 2 h. These results should be useful to the aquaculture industry, where anaesthesia is necessary for a range of activities.     

Pharmacokinetics of oxolinic acid in gilthead sea bream, Sparus aurata L.

This is the first study on the pharmacokinetic parameters of oxolinic acid (OA) in gilthead sea bream, Sparus aurata L. The kinetic profile of OA was studied after a single intravascular injection (20 mg kg⁻¹) in 100 g fish at 20 °C. The distribution half-life ( t _1/2α) and the elimination half-life ( t _1/2β) of the drug were found to be short (0.51 and 12.60 h, respectively). The drug penetration from the plasma to the tissues was adequate as the apparent volume of distribution of the drug at steady-state ( V _d(ss)) was found to be 2.11 L kg⁻¹. The mean residence time ( MRT ) of OA was short (14.25 h) and the total clearance rate ( Cl _T) of the drug was low (0.15 L kg⁻¹ h⁻¹). The bioavailability ( F %) of OA following oral administration (30 mg kg⁻¹) was also low (14%). Maximum values were observed for muscle at 0.5 h after injection, with levels declining as with subsequent sampling. At the first two time points (0.5 and 1 h) plasma levels of OA were higher than muscle, however, the reverse was evident for subsequent samples. Following oral administration, highest muscle levels were found at 16 h and, with the exception of the 24-h sampling, muscle OA concentrations were higher than plasma at all time points. The fast elimination of OA suggests short withdrawal times with reference to human consumption of treated fish.     

Comparison of lipid-walled microcapsules and lipid spray beads for the delivery of water-soluble, low-molecular-weight materials to aquatic animals

Microparticles (< 40 μm diameter) composed of 600 mg g⁻¹ tripalmitin/400 mg g⁻¹ fish oil were used to encapsulate the low-molecular-weight (mol. wt 460) antibiotic oxytetracycline in the form of either oxytetracycline hydrochloride (OTC.HCl) or oxytetracycline hemicalcium salt (OTC.HEM). Dry, finely ground particles of core material were encapsulated in spray beads. Dissolved core material was encapsulated in lipid-walled microcapsules.
Oxytetracycline (OTC) was most efficiently delivered (≈ 46.5 mg g⁻¹ lipid after 24 h suspension in seawater) as a hemicalcium salt in spray beads. Lipid-walled microcapsules were most efficient for delivering OTC (≈ 8.7 mg g⁻¹ lipid) as OTC.HCl dissolved in 0.2  M HCl at a concentration of 300 mg mL⁻¹.
Spray beads containing OTC.HEM were very stable over 1 month in storage. Lipid-walled microcapsules containing aqueous OTC.HCl lost ≈ 30% of their core material during storage. Freeze-drying of both microparticle types did not improve storage of spray beads, but showed promise for reducing leakage from lipid-walled microcapsules during storage and delivery to suspension feeders.     

Improved Seed Production of Goldstriped Amberjack Seriola lalandi under Hatchery Conditions by Injection of Triiodothyronine (T3) to Broodstock Fish

Survival of the seed of goldstriped amberjack Seriola lalandi was consistently enhanced by intramuscular injection of triiodothyronine (T₃) to the broodstock fish at a dose of 20 mg/kg body weight. Survival rates at the time of transfer to net cages (35 d after hatching) were 2.6–5.0% for the T₃ treatment while only 0.3–2.1% for the control. Survival rates 36 mo after hatching was estimated to be 12 times higher in the T₃-treated group (1.1%) than in the control (0.09%). T₃ concentration in newly spawned eggs increased from control levels of 0.3–1.0 ng/g to 68–127 ng/g 2 d after injection and subsided with successive spawns. T₃ concentration in the treated larvae was about 360 times higher than in the control upon hatching (29 np/p vs 0.08 ng/g), but became indistinguishable from the control 6 d after hatching. These results indicate injection of T₃ to the broodstock of S. lalndi to be of practical value in aquaculture of the species.     

Effects of different feeding level on the growth, feed efficiency and body composition of juvenile mangrove red snapper, Lutjanus argentimaculatus (Forsskal 1775)

The effects of several feeding levels (1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% and 4.5% of body weight per day, BW day⁻¹) on the growth, feed efficiency and body composition of juvenile Lutjanus argentimaculatus (body weight 27.1 g) were examined. Fish were fed a test diet (40% protein, 18.4% lipid and 13.4 kJ g⁻¹) for 75 days in three equal meals. Weight gain and specific growth rate increased with increasing feeding level up to 2.5% BW day⁻¹, after which no significant improvement in growth was observed. The feed efficiency, protein efficiency ratio, retention of protein and digestibility of nutrients did not differ for fish fed 1–2.5% BW day⁻¹, but decreased significantly when feeding levels were increased above 3% BW day⁻¹. The chemical compositions of whole fish or body organs were significantly affected by the feeding level. The condition factor, mesenteric fat, hepato- and viscerosomatic indices were higher in fish fed 2.5–4.5% BW day⁻¹. The cholesterol, triglycerides and haematocrit values were similar among treatments, except that high levels of plasma lipids were recorded in fish fed at 2.5% BW day⁻¹. Taking into consideration the growth, feed efficiency and body composition data attained in this study, a feeding level of 2.5% BW day⁻¹ is recommended for juvenile L. argentimaculatus weighing between 27 and 140 g.     

Pharmacokinetics of Dietary 13C-Labeled Docosahexaenoic Acid and Docosapentaenoic Acid in Red Sea Bream Chrysophrys major

The objectives of this study were to investigate: 1) the pharmacokinetics of dietary docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA) using ¹³C-labeled fatty acids; 2) the interorgan transport of DHA in the red sea bream by monitoring the DHA level of several organs; and 3) the relationship between the plasma DHA level and optimum dietary DHA level in the plasma of the red sea bream Chrysophrys major . For this purpose, a mixture of 38.5% of [¹³C]DHA, 8.5% of [¹³C]DPA, and 4.2% of [¹³C]palmitic acid were given to the red sea bream at dose level of 8.0, 16.0, and 47.9 mg/kg by a single oral administration. For [¹³C]DHA, the maximum plasma concentration (t_max) occurred at 2.00–3.00 h after the oral administration. The peak plasma concentration (C_max) and the area under the plasma concentration-time curve to 24 h (AUC_0-24 for [¹³C]DHA level linearly increased with respect to dosage. [¹³C]DHA appeared in each organ (plasma, erythrocyte and the fat body of the orbit, liver, intestine, skin, brain, heart and muscle) at 0.5 h and was observed until 24 h. From the values determined for the pharmacokinetic parameters, the range of the effective plasma DHA level for normal growth of the red sea bream was suggested to be between 21.0 and 40.3 μg/mL. For [¹³C]DPA, the AUC_0-24 and C_max values also linearly increased with the dosage, but t_max did not depend on it.     

Effect of different synthetic gonadotrop-releasing hormone analogues and their combinations with an anti-dopaminergic compound on the reproduction performance of sterlet (Acipenser ruthenus L.)

In this study, three synthetic gonadotrop-releasing hormones (GnRH) (azagly-nafarelin; des-Gly¹⁰-( d -Ala⁶)-LH-RH; and des-Gly¹⁰-( d -Phe⁶)-LH-RH) either alone or in combination with metoclopramide were used to induce reproduction of sterlet. The GnRH analogues were applied in a single dose of 40 μg kg⁻¹ of female and 20 μg kg⁻¹ of male body weight. Metoclopramid was administered in a simultaneous injection of 10 and 5 mg kg⁻¹ of body weight for females and males respectively. There were no significant differences in the ovulatory responses of females; ovulation rates varied between 57% and 80%, and at the temperature of 15.5–16.0 °C about 30–34 h were required for final maturation, when eggs of 17.3±1.3% of body weight were stripped. However, the fertilization rates of the des-Gly¹⁰-( d -Phe⁶)-LH-RH-treated groups were significantly lower than that in the other treatment. In males, the combination of the above peptidergic hormones with metoclopramide gave significantly better results than their single application. The results demonstrate that the final stage of gamete maturation in sterlet may be achieved by several hormonal means. The possibility of using new GnRH analogues without dopamine antagonists yields new perspectives for induced breeding of sturgeons, which have particular importance in the light of meat and roe (caviar) production for human consumption.     

Protective properties of egg yolk IgY containing anti-Edwardsiella tarda antibody against paracolo disease in the Japanese eel, Anguilla japonica Temminck & Schlegel

Abstract. Immunized hens are known to contain a high level of immunoglobulin Y (IgY) in their egg yolk. In this study, the present authors obtained anti- Edwardsiella tarda IgY (containing 20% specific IgY, agglutination titre, 1:128) from hens vaccinated by injection with formalin-killed bacterin. The IgY was stable against eel digestive factors, and therefore, was orally administered with viable E. tarda to the Japanese eels and the efficacy of protection against E. tarda infection was evaluated. Orally administered IgY at a dose of 400mg fish^-1 cleared E. tarda inoculated simultaneously at 10^5–6 CFU fish^-1 from the intestine within 24h. Moreover, orally administered IgY at doses of 200 and 400mg fish^-1 inhibited the penetration of E. tarda inoculated simultaneously at 10^4–6 CFU fish^-1 into the liver and kidney via the damaged intestine. The fish orally administered with IgY showed reduced mortality. These results suggest that egg yolk containing anti- E. tarda IgY is effective in preventing edwardsiellosis.     

Effects of water discharge and temperature on the seaward migration of anadromous browntrout, Salmo trutta, smolts

Abstract – The smolt run of anadromous brown trout ( Sulmo trutta ) in a Norwegian river was studied for three consecutive years. The main run occurred in a period of 7–10 days in the middle or second half of May. Support was found for the hypothesis that high water discharge and temperature triggered the run. Few smolts descended when the discharge was low (<50 m³· s⁻¹) and the water temperature was below 4°C. The maximum number were caught when the discharge was moderate (70–150 m³· s⁻¹) and the water temperature high (68°C). The relative importance of these factors varied from year to year. The first-year discharge explained 38% of the variation in the number of smolts migrating. Discharge and temperature together explained 61% in 1992 and 28% in the second and third year, respectively.     

Effect of Ultraviolet Irradiation on Sperm of the Left-eyed Flounder, Paralichthys olivaceus

In this study, at proper dosage of ultraviolet (UV) irradiation (180   sec: 36,000   erg/mm²), sperm chromosomes of left-eyed flounder, Paralichthys olivaceus , were inactivated, while spermatozoa maintained ability to move and inseminate eggs. Gynogenetic haploids were detected by morphological observation, chromosome counting, and flow cytometer analysis. The ultrastructure of treated sperm was observed under scanning electronic microscope (SEM) and transmission electronic microscope (TEM). The results showed that after being irradiated at lower dosage of irradiation (0–180   sec: 0–36,000   erg/mm²), the surface structure of spermatozoa was not affected by UV irradiation, while the inner structures including membrane system and karyoplasm denseness of treated spermatozoa were little changed. However, obvious changes were observed in their membrane system, mitochondria, and nucleus if the dosage of irradiation increased to 240   sec: 48,000   erg/mm² or 300   sec: 60,000   erg/mm². The sperm survival rates did not change at the lower dosages of the UV irradiation (0–180   sec: 0–36,000   erg/mm²) but decreased as the irradiation dosage increased. The motility of treated sperm was lower than that of control group in general but did not change with UV irradiation dosage increasing at the certain range of 0–300   sec: 0–60,000   erg/mm².     

Angling pressure, yield and catch per effort of grayling, Thymallus thymallus (L)., and brown trout, Salmo trutta L., on the rivers Glomma and Rena, southeastern Norway

Abstract Postal questionnaires, interviews and accurate reports from anglers were used to study angling activity, yield and catch per effort of grayling, Thymallus thymallus (L.), and brown trout, Salmo trutta L., on three stretches of the regulated river Glomma and two stretches of its tributary, the river Rena in southeastern Norway. Angling activity was expressed as hours angling per kilometre of river and varied from 364 (CL 245–598) to 1337 (CL 912–1991) h km^-1. Grayling and brown trout dominated the catches. The catches were estimated between 476 (CL 334–659) and 753 (CL 517–1155) grayling and brown trout per kilometre river stretch. The mean weights were estimated between 216 and 353 g for grayling, and 260 and 395 g for brown trout. The yield of grayling and brown trout was estimated between 8.7 (CL 6.1–12.4) and 46.4 (CL 34.9–62.3) kg ha^-1 yr^-1. The quotient grayling/brown trout in the catches varied between 0.41 and 5.1, and was found to be significantly negatively correlated with angling effort ( r = - 0.838, P <0.05). Catch per effort was estimated between 132 (CL 82–218) and 382 (CL 287–513) g h^-1, and was also negatively correlated to angling effort, according to: Catch per effort (g h^-1) = - 0.210 × effort (h km^-1) + 405 ( r = and 0.899, P <0.02).
Angling activity in earlier years was determined from number of permits sold where data were available. On stretches where angling activity was moderate, there was a tendency towards increase, whereas on stretches where activity had been high for several years, the activity seemed to have stagnated, indicating that a saturation had been reached.     

Potential benefit of clove oil sedation on animal welfare during salmon smolt, Salmo salar L. transport and transfer to sea

The purpose of this study was to determine the effect of clove oil (4.0 mg L⁻¹) sedation, compared with non-sedation, on the primary (plasma cortisol), secondary (osmoregulation) and tertiary (mortality) stress responses in Atlantic salmon smolts during transport and transfer to sea. Clove oil sedation during on- and off-loading sufficiently reduced the primary stress response to lower mortality (2.1%) during transfer to sea compared with unsedated fish, which experienced a mortality rate above 12.2%. The unsedated fish experienced an acute mortality that stabilized only 6 days after the transport. None of the secondary stress responses measured in this experiment could contribute towards explaining this phenomenon, with the possible exception of plasma magnesium (Mg²⁺). Plasma Mg²⁺ differed between the groups; while plasma Mg²⁺ in the clove oil sedated group returned to pre-stress levels 72 h after transport, the unsedated group showed no such recovery even 1 week after transport, which may indicate a disturbance in the hydromineral balance, and provides a plausible explanation for the delayed mortality in this group. Eugenol-based anaesthetics appear to be promising as a stress-reducing sedative for Atlantic salmon smolts, and, if used properly, this chemical could improve animal welfare and survivability during and after common aquaculture-related incidents.     

Pharmacokinetics and tissue distribution of oxytetracycline in sea bass, Dicentrarchus labrax, at two water temperatures

A pharmacokinetic study of oxytetracycline (OTC) following an intravascular administration (40 mg/kg) was carried out in sea bass, Dicentrarchus labrax (110 g), at 13.5 and 22 °C water temperature. Blood, muscle and liver samples were taken at 1, 2, 4, 8, 16, 32, 64 and 128 h post-injection. The plasma data were conformed to a two-compartment model. The kinetic profile of the drug was found to be temperature dependent. The absorption half-life (t_1/2) of OTC was 0.98 and 0.192 h at 13.5 and 22 °C, respectively, whereas the elimination half-time (t_1/2β) of the drug was 69 h at 13.5 °C and 9.65 h at 22 °C. The apparent volume of distribution of the drug at steady state [V_d(ss)] was 5.62 l/kg at 13.5 °C and 2.59 l/kg at 22 °C. The mean residence time (MRT) of OTC was found to be 37.7 h at 22 °C and 71 h at 13.5 °C. The total clearance of the drug (CL_T) was calculated to be 73.5 and 68.7 ml/kg/h at 13.5 and 22 °C, respectively.

Liver levels indicated higher OTC values than respective muscle levels at all time points and for both temperatures. The elimination of OTC from tissues tested was faster at the high temperature, whereas the drug was eliminated faster from liver compared to muscle when comparisons are made at the same temperature.     

Evaluation of practical diets containing different protein levels on gonad development of female redclaw crayfish Cherax quadricarinatus

The effect of five experimental diets with different crude protein content (220, 270, 330, 390 and 450 g kg⁻¹) on gonad development of female Cherax quadricarinatus was tested under laboratory conditions. After 70 days, a significant linear relationship indicated that higher concentrations of protein and carbohydrates in the hepatopancreas were produced as the dietary crude protein increased ( P  < 0.05). There were significant responses of the gonadosomatic index, hepatosomatic index, biochemical composition of the gonad (protein, lipids, carbohydrates and energy) and frequency of secondary vitellogenic oocytes to dietary protein level, as indicated by significant fits of the quadratic equation to the observed experimental data. The optimal response of the criteria parameters corresponded to levels of crude protein in the range 284–355 g kg⁻¹. Overall, 330 g kg⁻¹ crude protein with a protein : energy ratio of 15.6 mg kJ^–1 was considered the most adequate concentration of dietary protein for gonad development and biochemical composition in female redclaw crayfish.     

The interactive effects of dietary protein and energy on feed intake, growth and protein utilization of juvenile mulloway (Argyrosomus japonicus)

The objectives of this study were to describe the interactive effects of varying digestible protein (DP) and digestible energy (DE) contents on the feed intake, growth, protein utilization and whole body composition of juvenile mulloway ( Argyrosomus japonicus ) and to determine the optimal DP : DE ratio for growth. This was achieved by feeding mulloway diets containing one of four different DP levels (250–550 g kg⁻¹) at two DE levels (16 or 21 MJ kg⁻¹). Juvenile mulloway were stocked at each of two different sizes (70 or 200 g) in triplicate groups for each dietary treatment and fed twice daily to apparent satiation over 58 days. The results indicated that feed intake was not governed solely by energy demands but was also dependant on the DP content of the diet. Protein utilization did not improve with diets containing decreasing protein and increasing lipid content indicating that mulloway have a limited capacity to spare DP. Optimal DP content was found to be 444–491 g kg⁻¹ depending on the DE content of the diet and the size of mulloway and is within the range reported for other sciaenid species. The use of formulated diets with 28.6 g of DP MJ DE⁻¹ will achieve optimal growth and protein deposition for 70–275 g mulloway.     

Effect of Genistein on the Growth and Reproductive Function of Male and Female Yellow Perch Perca flavescens

We studied the effect of genistein, a weak estrogenic compound found in soybean products, on the growth and reproductive development of yellow perch Perca flavescens . Four diets were prepared: control, estradiol-17β (E₂) at 10 μg/g diet (E10), and genistein at 7.5 and 0.75 mg/g diet (G7.5 and G0.75). Fish (initial weight = 13–15.5 g and initial total length = 105–111 mm) were fed to excess for 63 d. The E10 diet promoted weight gain in yellow perch of both sexes, whereas the G7.5 diet decreased weight gain in females. The growth of the G0.75 group was not different from either the E10 group or the control group. Among females, fish fed the E10 diet had the lowest plasma concentration of E₂ 36 h after the last feeding of the study. The plasma concentration of E₂ did not differ among the males from the four treatments. The E10-treated fish of both sexes had increased plasma concentration of alkali-labile phosphoprotein phosphorous (ALPP) in both sexes, indicating that vitellogenesis had been induced. Neither genistein diet increased plasma (ALPP) concentration. Male but not female yellow perch fed the E10 diet had significantly lower gonadosomatic indices compared to control and genistein groups. These results suggest that genistein may have a positive effect on growth in yellow perch, but no apparent estrogenic effects on reproductive function.