Jean-Noël Gardeur

Reproductive cycle and plasma levels of sex steroids in female Eurasian perch Perca fluviatilis

Abstract From April 1995 to April 1996, the annual reproductive cycle of the Eurasian perch Perca fluviatilis was studied at the Fishfarming Lindre Center (Moselle, France). At monthly intervals (at intervals of 10 days during the periovulatory period), 5 females were caught and dissected. From sampled organs, the gonado-, hepato- and viscerosomatic indexes (GSI, HSI, VSI) were calculated, oocyte diameters (OD) and the plasma levels of testosterone (T), 17β-estradiol (E 2 ), 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and protein-phosphorus (PPP) were measured. After the sexual resting period observed from May to August (GSI 2 , 17,20β-P and PPP were low during the sexual resting period. E 2 and PPP levels increased significantly at the onset of the oogenesis in September, then the E 2 level raised abruptly in November (3–4 ng · mL −1 ). In December, the T level increased rapidly to 15–20 ng · mL −1 . The testosterone, E 2 and PPP levels remained very high until spawning, indicating the existence of active vitellogenesis. The highest HSI (2.1–2.2 %) recorded in winter confirmed this. During the periovulatory period, a peak of E 2 (4 ng · mL −1 ) appeared, whereas T level diminished. In this study, 17,20β-P levels remained low (0.2–0.6 ng · mL −1 ) and relatively constant. No 17,20β-P peak was observed during the periovulatory period. Sampling at 10 day intervals was probably inadequate to specify the hormonal variations related to the final oocyte maturation and the ovulation.

Induction of out-of-season spawning in Eurasian perch Perca fluviatilis: effects of rates of cooling and cooling durations on female gametogenesis and spawning

Abstract This study was designed to determine the influence of different thermal conditions during an out-of-season reproductive cycle on gonad recrudescence, plasma steroid levels (testosterone and estradiol), vitellogenin (VTG) concentrations and spawning in Eurasian perch ( Perca fluviatilis ) females. The experiment was performed in 450-l square polyester indoor tanks located in two rooms equipped with controlled light and temperature devices. Four thermal regimes were tested with two different rates of cooling from 21 to 6 °C, 3 weeks (3w) or 6 weeks (6w), and two different durations at 6 °C, 3 months (3m) or 5 months (5m). The photoperiod was fixed at LD 12:12. A long cooling period (6w) resulted in greater gonadosomatic index (GSI) (3.6±0.5%) correlated with a larger oocyte diameter (787.9±25.1 μm). The plasma levels of testosterone (13.63±1.18 ng ml −1 ) in the former groups were higher than in the short cooling period groups (6.82±0.9 ng ml −1 ). A longer duration at 6 °C (5m) resulted in higher GSI (14.8±1%), plasma testosterone levels (26.2±0.4 ng ml −1 ) and plasma protein phosphorus (PPP, 1.33±0.3 μg ml −1 ). The fish from the 6w 5m batch showed the highest plasma estradiol and testosterone levels, whereas the 3w 5m group showed the largest GSI. At the end of the experiment, several spontaneous out-of-season spawnings were collected in batch 6w 5m. Biopsy showed that most oocytes from groups 3w 5m and 6w 5m females were mature (migration of the germinal vesicle from central position), whereas few females showed a beginning of migration in groups 3w 3m and 6w 3m, suggesting that the gonad development and reproductive success of Eurasian perch mainly depends on the chilling duration (long cold period) rather than on the cooling one, in order to obtain out-of-season spawning.

Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species

Based on an extensive literature search (1,000 references), the objectives of the present study were to establish a numerical clustering of temperate freshwater fish based on their reproductive traits and to evaluate whether it was possible to extrapolate zootechnical knowledge among species belonging to the same cluster. About 65 species were classified into ten homogeneous clusters from the analysis of 29 reproductive traits, among which the most important were temperature during spawning, egg incubation and larval rearing, degree-days for incubation, larval size upon hatching, spawning season, and parental care. From this typology, a rather regular continuum of reproductive clusters emerges with two obvious endpoints. Between these two extremes, species could be ordered chiefly according to temperature requirement, spawning season and parental care. In conclusion, this new typology, differing significantly from all others proposed earlier, may now serve as a possible framework to help enhancing the domestication of new species by comparison to species belonging to the same cluster.

The relationship of oocyte diameter and incubation temperature to incubation time in temperate freshwater fish species.

Based on the analysis of six egg variables and incubation temperature of 65 temperate freshwater fish species, the possible relationships between oocyte diameter, incubation time and incubation temperature were reassessed and compared to the results obtained from marine fishes. Most freshwater species have eggs (mean +/-s.d. 2.19 +/- 1.52 mm) larger than marine species, that are chiefly demersal and develop stuck to various substrata, such as plants or rocks. A strong negative relationship was found between incubation time (t, days) and incubation temperature (T, degrees C): t = 186.23e(-0.197T) (r(2)= 0.87). A strong dependence of incubation time on oocyte diameter (Ø, mm) and incubation temperature was also found and was defined as: log(10)t= 3.002 + 0.599 log(10)Ø - 1.91 log(10) (T + 2), which explained 92% of the variance of the data set. Five major groups of species were defined based on the principal component analysis (PCA) of four quantitative variables. There were two distinct groups of salmonids, displaying demersal and non-adhesive eggs with a long incubation time at low temperature, the eggs of which required a high number of degree-days. There was a large group of species possessing small, mostly demersal and adhesive eggs developing at high temperature during a short period of time, and requiring a low number of degree-days. Between these two extremes, there was a fourth group displaying intermediate values and a fifth group including three species with large, adhesive and demersal eggs incubating at high temperatures during a short period of time. The burbot Lota lota displayed an unusual combination of variables compared to the remaining species in the data set.

Effects of geographic source, rearing system, and season on the nutritional quality of wild and farmed Perca fluviatilis.

The effects of season, geographic source (Lake Geneva, Rhine River), and rearing system (extensive, semiextensive, and intensive systems) on the lipid content and FA composition of fillets of Perca fluviatilis were studied. Significant differences in the total lipid content were found between fish coming from the Rhine River and Lake Geneva (1.21 and 1.48%, respectively). Seasonal effects were investigated quarterly for perch sampled in the Rhine River. Intensively reared perch displayed a higher lipid content (1.48%) than the other farmed perch, i.e., 1.26% for a semiextensive system and 1.16% for an extensive system. No significant difference in lipid content was found (i) between lacustrine fish and intensively reared fish or (ii) among fish from the Rhine River and the semiextensive or extensive rearing systems. The main FA were 22∶6n−3 (DHA, 21.3–37.1% of total FA), 16∶0 (17.7–20.2%), 20∶5n−3 (EPA, 9.2–13.2%), 18∶1 (8.0–11.5%), 20∶4n−6 [arachidonic acid (ARA), 1.9–10.7%], 16∶1 (4.3–6.0%), and 18∶2n−6 (2.1–6.0%). In comparison with perch coming from the Rhine River, the lacustrine fish were characterized by higher total n−6 PUFA and a lower proportion of both total monounsaturated FA (MUFA) and total n−3 PUFA. Among rearing systems, extensively farmed fish had higher n−6 PUFA and lower n−3 PUFA contents. Wild fish showed higher ARA and 18∶2n−6 than farmed fish. They also had significantly more EPA (12.5–13.2%) than farmed perch (9.2–10.9%). For DHA no difference existed between (i) the lacustrine fish (31.9% of total FA) and the intensively reared fish (33.0%) and (ii) the Rhine (37.1%) and semiextensively reared fish (36%). Effects of size, diet composition, and environmental conditions on the total lipid contents and FA composition are discussed.

Pesticide pressure and fish farming in barrage pond in northeastern France. Part III: how management can affect pesticide profiles in edible fish?

PurposeThe quality of fish produced in ponds needs to be ensured. Indeed, pond is often strongly connected to an agricultural watershed, and pesticides are a main health and environmental issue of concern. In this context, the purpose of this study is to highlight the management practices which could impact the pesticide contamination profiles in edible fish and to give recommendations for better practices.MethodsA principal component analysis, coupled to a hierarchical cluster analysis, was performed to evaluate temporal evolution of contamination profiles and to assess variability among fish species and among sites according to watershed characteristics. The explicative variables correspond to muscular concentrations of pesticides (azoxystrobin, clomazone, diflufenican, carbendazim, isoproturon, metazachlor, napropamid) in three species of fish (Perca fluviatilis, Cyprinus carpio and Rutilus rutilus), caught in five ponds during two sampling campaigns. Management data are added variables in order to discuss about parameters suspected to be implicated in the contamination profiles recorded.ResultsThis work shows that high amounts of pesticides applied, short crop rotation durations and bare soil practices led to contamination of sediments and fish and were associated to a “bad” management of watershed. Breeding fish that had low masses and establishing the fishing period at the end of winter seemed to be “bad” management of pond. Aggravating topological parameters were big watershed coupled to small pond and high proportions of sand soils in the watershed.ConclusionsReducing amounts of pesticide used (e.g. policy agency plans, farmer acceptance), favouring long-term rotations and inter-cultures, adapting pond creation and fish farming practices to watershed management and topography all could reduce pesticide levels in edible fish and contribute to a better sustainability of the extensive fish farming in pond.

Growth heterogeneity in rearing sea bass (Dicentrarchus labrax): test of hypothesis with an iterative energetic model.

This study aimed at modeling the relative importance of food intake on growth heterogeneity among cultured sea bass (Dicentrarchus labrax). First, we designed an individual growth model comprising five compartments (Energy intake, Losses, Net Energy, Recovered Energy and Maintenance). This model was calibrated with a first experiment carried out in eight tanks; A total of 130 juveniles (11 g) per tank were fed by a self-feeder (84 days, 20°C, 16L : 8D, 30 g NaCl/l). A second experiment was performed to better understand the relation between individual food intake, individual growth and growth heterogeneity, using the model as a tool for a hypothetico-deductive approach on growth heterogeneity (135 passive integrated transponder-tagged fish, same rearing conditions as above and individual food intake measured by X-ray every 14 days). The tested hypotheses were that food intake was (a) homogeneous, (b) proportional to the fish weight (i.e. to W1.00) X-ray (c) proportional to W0.66 and (d) reflected by the X-ray measurements of food intake. For each hypothesis, a simple linear regression between experimental and simulated results was produced. The Fitness indicators of these analyses, together with their confidence intervals (calculated by bootstrapping), allowed testing the relevance of these hypotheses. The analysis indicated that growth heterogeneity was largely accounted for by individual variations of food intake, as revealed by the X-ray analysis, and that food intake was proportional to W1.00, which suggests a dominance hierarchy where small fish are incapable of feeding maximally.

Concept and Determinism of Quality in Percid Fishes

The development of the Percid fish industry calls for reflection on the concept and determinism of quality. This chapter starts with some general considerations illustrating the evolution of quality perception over time. The sense of the word ‘Quality’ is now polysemic; this brings together information about fish characteristics according to their origins (wild versus farmed), but also consideration on how fishes are produced. The complex picture of quality in Percid fishes is here illustrated with the study of nutritional, technological, sensory and sanitary components. We show on the basis of numerous studies that the determinism of quality is multifactorial. Quality components are thus governed by several biological (species, age, genotype, level of domestication…) and environmental (water characteristics, diet, season..) factors. However the quality objectives in Percid Fishes may vary depending on the stakeholders (fish farmer/fisherman, processor or consumer). As far as possible, the various expectations need to be addressed under the target values for the different quality components. In conclusion, we propose the adoption of multifactorial approaches to provide best information in understanding of determinism quality in Percid fishes.