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All issues No 427 (2026) Knowl. Manag. Aquat. Ecosyst., 427 (2026) 1 Full HTML
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Knowl. Manag. Aquat. Ecosyst.
Number 427, 2026
Multidisciplinary solutions for conservation
Article Number 1
Number of page(s) 11
DOI https://doi.org/10.1051/kmae/2025030
Published online 30 January 2026

© F. Teletchea et al., Published by EDP Sciences 2026

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License CC-BY-ND (https://creativecommons.org/licenses/by-nd/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. If you remix, transform, or build upon the material, you may not distribute the modified material.

1 Introduction

Up to the early 2000s, it was supposed that the metropolitan French territory hosts about 80 freshwater and diadromous fish species, among which one-third had been introduced in the last century (Keith and Allardi, 1997). Yet, this number increased strongly in the recent years to reach more than 120 species, partly due to the introduction of new fish, such as gobies, but mostly due to the revision of the French fish species fauna based on integrative taxonomy (Keith et al., 2020; Teletchea, 2020; Denys et al., 2024). Hence, nine genera have been revisited so far, with the addition of 26 new species, most of them being endemic to mainland France (Denys et al., 2024).

Among those revised genera are pikes Esox. For at least two centuries, the taxonomy of the Esocidae was considered well-known, including seven species occurring throughout North America and Eurasia (Raat, 1988; Crossman, 1996). Among these seven species, Northern pike E. lucius Linnaeus 1758 is the most common esocid worldwide, with a circumpolar distribution covering both North America and Eurasia (Raat, 1988; Denys et al., 2014). Besides, due to its high socio-economic interest for recreational and commercial fishing as well as aquaculture (Raat, 1988; Arlinghaus et al., 2018), this species is one of the best studied fish species, particularly concerning its reproduction and early life stages (Teletchea et al., 2007; Pospisilova et al., 2019; Réalis-Doyelle et al., 2022). This species is also regularly stocked in numerous water bodies including those where it is not native (e.g., Cucherousset et al., 2021). In France, Northern pike was considered to be the only esocid present, native to the Rhine, Seine, Loire (except in Brittany), and Rhône drainages (Denys et al., 2014; Keith et al., 2020). Yet, a taxonomic revision has allowed the discrimination of another pike species, the Aquitanian pike E. aquitanicus Denys, Dettai, Persat, Hautecoeur & Keith, 2014, an endemic species of Southwestern France from the Charente to the Adour drainages (Denys et al., 2014). However, the ubiquist species E. lucius was also introduced in these catchments at least since the 50s with the development of aquaculture (Keith et al., 2020).

The two French pike species differ according to morphological, mitochondrial and nuclear data (Denys et al., 2014; Denys et al., 2018; Jeanroy and Denys, 2019). Concerning morphology, the most obvious differences are that the Aquitanian pike possesses a marbled coat and a shorter snout than Northern pike (Denys et al., 2014). Yet, even though it is supposed that Aquitanian pike should have similar biological traits than Northern pike, almost nothing is known about the biology of this new pike species, especially concerning its early life stages (Denys et al., 2014). The breeding season is supposed to begin in February according to Chimits (1956), during which Aquitanian pike comes to spawn in the channels of marshy areas at the source of streams or in lagoons (Glize, 1993).

E. aquitanicus is currently listed as Vulnerable according to the French IUCN Red List of Threatened Species, particularly because of the degradation of its habitat – especially its breeding areas – and the introduction of E. lucius (Keith et al., 2020). It is therefore important to better known the species biology and ecology to establish effective conservation and management policies. In this context, the four main goals of the present study were to (i) obtain the first morphological data on the early life stages of Aquitanian pike, and particularly the development of the snout length, (ii) test the effects of temperature on their survival and development, (iii) compare the results with the Northern pike, and (iii) produce a few individuals to exhibit them at the Aquarium of Limoges in order to promote the conservation of this species to the public.

2 Material and methods

2.1 Sampling of wild eggs

There is currently no commercial farming of Aquitanian pike, and no precise information were available about how and when to perform the artificial reproduction of this species. Therefore, we decided to sample eggs in situ in two sites located in the Landes department (Southwestern France), where it was demonstrated that only this species was present; thus, no risk of hybridization with common pike (Fig. 1). The first site is the marsh of Uza (Latitude: 44.025567, Longitude: −1.186314), a hunting reserve, located in a peat bog where the Vignac brook flows upstream of the pond, with water bodies on either side of the main stream that are connected to it during flood periods. The second site is the Plaine aux Pigeons in the township area of Lit-et-Mixe (Latitude: 44.052100, Longitude: −1.266470), a marshland managed by the Landes Hunting Federation and bordered by a brook called “Courant mort”, which feeds tons of water for waterfowl hunting. Both sites are located within the Courant de Contis watershed (Fig. 1).

As pikes are phytophil, the harvesting method consisted of scraping the base of aquatic grass-like plants located on the inshore of the pond towards the water surface, using a landing or a kick net. Sampling was done three successive years: the first one from the 3rd to the 19th February 2021 ten times (from 9:00 a.m. until 4:30 p.m.), the second one from the 10th to the 13th of January 2022 as well as from the 31st January to the 1st February 2022, and the last one the 2nd February 2023. Once collected, the eggs were held and oxygenated in a bottle with water from the site until being sent by post to the University of Lorraine in Nancy (2021, 2022) and Aquarium of Limoges (2023), with an expected delivery time of less than 24 h. Upon their arrival, the water temperature was set at 12 °C, close to that observed at the sampling sites, and remained at this value until the end of the incubation period. Yet because we could not determine precisely when spawning had occurred and therefore how old the embryos were, we only start our experiments at hatching.

thumbnail Fig. 1

Distribution area of the two pike species in France (Esox aquitanicus in red, Esox lucius in its native area in blue and introduced in green) (modified and adapted from Keith et al., 2020; Royer et al., 2024), with the sampling locations of Aquitanian pikes breeding areas in the Courant de Contis watershed (Landes department; southwestern France): the Plaine aux Pigeons at Lit-et-Mixe and the marsh of Uza; credits photos: G. Denys.

2.2 Morphological description of the early life stages

As eggs are not strictly spherical (Teletchea et al., 2007), the diameter was calculated from the mean of two perpendicular diameters. Eggs were also observed to identify the stage of embryogenesis following Pospisilova et al., 2019 to approximate the time of fecundation and hatching. At hatching, and then once a week, five larvae individually reared in a petri dish to avoid potential cannibalism frequently observed in Northern pike (Kucska et al., 2007), were randomly sampled and photographed to follow the morphological development, and calculate the relative length of the snout (SnL) compared to the eye diameter (EyD) (Fig. 2).

thumbnail 2

Snout length (SnL) versus horizontal eye diameter (EyD). Drawing by Guillaume Rech.

2.3 Experimental conditions for testing the effect of temperature on the survival and development of early life stages

Eggs or recently hatched larvae were evenly distributed in three trays in each of the five incubators located at the Université of Lorraine in Nancy to test the effect of temperature (6, 9, 12, 15 and 18 °C), first on the endogenous feeding period of larvae (i.e., from hatching up to the full resorption of the yolk sac) and then during 11 weeks post-hatching; for more information about the experimental design see Réalis-Doyelle et al. (2016, 2018, 2022). The temperature was applied as soon as all larvae hatched. The temperature was measured daily. Given the lack of any reference for the photoperiod and especially light intensity for this species, it was decided to leave the eggs, then the larvae, in the dark to limit stress. However, this decision was re-evaluated during the week 7, when the room's general lighting was used with a photoperiod of 8L/16D, i.e., from 9 a.m. to 5 p.m. Once the endogenous feeding period was over, it was decided to feed pike. According to Kucska et al. (2007), pike larvae are capable of feeding on a floating pellet, whether fed continuously or twice a day, while Hubenova et al. (2010) recommended a feeding frequency of four times a day. Hubenova et al. (2010) and Pasquet et al. (2016) fed larvae first with live brine shrimp Artemia salina (Linnaeus, 1758) nauplii, followed by inert feed, with a transition period between feed types (co-feeding). Therefore, we decided to feed larvae four times a day, first with live Artemia and then pellets. Because of the low number of larvae obtained, three larvae were randomly anesthetized, sampled and measured per tray at both hatching and when the yolk sac was fully consumed, and then each week post-hatching. After being photographed, larvae were returned to their respective trays. Measurements of nitrite and ammonium concentrations (in mg/L) began on March 19 (T4), one to three times a week (Monday, Wednesday and/or Friday), from April 7 (T7) to May 5 (T11).

2.4 Observations and measurements

Total length (TL) and observations for both the individual rearing and the experiment on the effect of temperatures were realized with a microscope (see Réalis-Doyelle et al., 2022). Besides, for the individual rearing, the larvae were photographed individually each week, using a binocular magnifying glass, to measure the development of the snout. Measurements were taken using GIMP software. The survival rate (SR) was calculated as follows: SR (%) = nf x 100 / ni, where ni and nf are the initial and final number of larvae, respectively, measured both at the end of the endogenous feeding period and each week. The duration of the endogenous feeding period, corresponding to the duration between hatching and when all yolk sac is consumed, was calculated per temperature. Daily growth was calculated by considering the duration (d), and TL using the following formula: DG (mm / d) = TLf – TLi / duration of the feeding period, with TL in mm and duration in days, i is hatching and f the end of endogenous feeding period. Then, larvae were measured each week.

2.5 Statistical analysis

Statistical analyses were performed using R (R Core Team, 2018). In this experiment, there is one quantitative dependent variable (total length or survival rate) for one quantitative independent variable (temperature, which has five modalities). We checked normality with the Shapiro Wilk test and variance homogeneity with a Levene test (R-package “car”; Fox and Weisberg (2019)), before choosing whether we could perform an ANOVA or a non-parametric Kruskall-Wallis test. Finally, the data were compared using a Tukey post hoc test.

2.6 Exhibiting the Aquitanian pike at the Aquarium of Limoges

Eggs sampled at the Plaine aux Pigeons in the township area of Lit-et-Mixe the 2nd February 2023 were sent to the aquarium by an express carrier. On their arrival, eggs were evenly distributed into six trays located in a specific aquarium (100 × 40 cm) with 20 cm of water depth. Based on our results of the first year of the project, the photoperiod was set as follows: 11L/13D; light was from 8 a.m. until 7 p.m. Larvae were fed, at least five times a day between 9:30 a.m. until 6:30 p.m., first Artemia enriched with Selco (Ocean nutrition) and then pellets and various food items were gradually added.

3 Results

3.1 Egg samplings and their use

A total of 392 eggs were collected in shallow waters among sharp-flowered rush Juncus acutiflorus Ehrh. ex Hoffm. (1791), common rush J. effusus (Linnæus., 1753) and bog pondweed Potamogeton polygonifolius (Pourr., 1788) at a temperature of about 12 °C (see also Denys et al., 2023), and sent by post in three batches. The first batch, comprising around 50 eggs, was collected from February 3rd to 4th 2021 and sent the last day, and arrived on the 6th in Nancy. The larvae hatched on the 7th and were only used to test an anesthetizing method (data not shown). The rare cases of cannibalism were observed on March 25, 46 days after hatching for this batch only (Fig. S1). The second batch contained 233 eggs, collected from February 4th to 8th 2021, before being shipped on the 8th and received at the laboratory the following day. They hatched from February 16th to 20th. Most larvae were evenly distributed into five incubators for the experiment on temperature, while 15 were put alone in modified petri dishes within a tray for the individual monitoring at 12 °C. The 2nd February 2023, about 100 eggs were collected in the bog pondweed and sent to the Aquarium of Limoges.

3.2 Morphological description of the early life stages

Eggs are yellowish, demersal, and sticky (Fig. 3); some particles were often stuck on them. For the first batch collected in February, 2021 the mean egg diameter was 2.81 ± 0.04 mm (n = 25). Among the 25 eggs observed on February 6th, heartbeats were visible for only one, while muscle contractions were observed for three embryos. The diameter of the second batch measured on February 15th 2021, was 2.71 ± 0.08 mm (n = 134). Some embryos were at the pre-hatching stage according to the Northern pike development table (Pospisilova et al., 2019). Finally, on February 18, 2021, the eggs of the second batch used for the individual monitoring had a diameter of 2.72 ± 0.06 mm (n = 15). In conclusion, all eggs combined measured 2.73 ± 0.08 mm (n = 174).

Larvae at hatching are characterized by a curved, transparent body with a light-brown coloration (Figs. 4, and 5). The curved trunk rests on a voluminous, ovoid yolk reserve. The head, bearing large eyes, is bent downwards at the anterior part of the yolk. With the exception of the pectoral fins, the other fins are not yet differentiated from the protopterygia. Melanophores are found on the dorsal side (and the upper part of the yolk bladder) but not on the ventral part, while pigments accumulate along the lateral line. The larval size at hatching, measured on February 18th, 2021 was 9.09 ± 0.24 mm (n = 14).

The morphological development of 15 larvae, reared individually at 12 °C, was followed during 11 weeks (Tab. 1, Fig. 5). Besides, we also calculated the snout growth in relation to eye size on the same 15 larvae. The snout was about half the size of the eye 15 days after hatching, and became larger than the eye at T9, just over two months after hatching (Fig. 6).

thumbnail Fig. 3

Egg of Aquitanian pike (from batch 1, photographs taken on February 6th, 2021). Egg diameter = 2.83 mm. Scale = 1 mm.
thumbnail Fig. 4

Larvae at hatching of the Aquitanian pike larvae (batch 2, from February 19, 2021). TL = 9.24 mm. Scale = 1 mm.
thumbnail Fig. 5

Morphological development of the Aquitanian pike during the first 11 weeks post-hatching (n = 15 larvae; reared individually in a petri dish) at 12 °C, see Table 1. Drawing by Guillaume Rech. Scale = 1 mm.
thumbnail Fig. 6

Evolution of the ratio of snout length compared to the eye diameter during 11 weeks at 12 °C (mean ± SD).
Table 1

Morphological development of the Aquitanian pike during the first 11 weeks post-hatching when reared at 12 °C (n = 15 larvae; reared individually in a petri dish), see Figure 5.

Table 2

Initial number of larvae per temperature tested, and per tray.

Table 3

Comparison of early life stages of Aquitanian common pikes. Data for common pike were taken from Teletchea et al. (2007), completed with those on-line here https://www.storefish.org/species/esox-lucius). Definitions of traits can be found here https://storefish.org/description.

3.3 Effects of five temperatures on the survival and development of the early life stages

Overall, 114 larvae were tested, ranging from 19 to 25 per temperature and between 3 and 10 per tray (Tab. 2). The overall survival rate was over 85% during the entire larval endogenous feeding period for all tested temperatures, with a maximum of 96% at 12 °C (Fig. 7A). No significant difference was found. Except at 6 °C, the larvae show a similar size at the end of the endogenous period (Fig. 7B). The endogenous feeding period lasted from 12 days at 18 °C to 36 days at 6 °C (Fig. 7C). Thus, daily growth increased fourfold between 6 and 18 °C (Fig. 7D).

During the first week (T1), most larvae were immobile, remaining either at the bottom of the tray or attached to the walls of the trays. This behaviour changed during the second week (T2) when the yolk sac resorbed and the larvae began to swim. However, larvae at 6 and 9 °C remained inactive throughout the experiment (T11). They swam only when a current was generated by sucking up and expelling water with a dropper pipette. Even the presence of food (nauplii or pellets) did not seem to make them reacted. After 11 weeks, the best survival rate was obtained at 12 °C with 61% (Fig. 8). For the other temperatures tested, values at 6, 9 and 15 °C were below 5%. At 18 °C, all larvae were dead, the last one died during week T6 (Fig. 8).

As for the end of the endogenous period, three larvae were randomly taken and photographed, for each of the 3 trays in the 5 incubators, bringing the total number of samples per week to 45. The total larval length at 12 °C had doubled in 8 weeks (Fig. 9). At the same time, the size of larvae at 15 °C tripled in 10 weeks, while at 6 and 9 °C, size changed little over the course of the experiment.

thumbnail 7

Effect of temperature on the survival rate (A), larval size (B), duration (C) and daily growth (D) during the endogenous feeding period, i.e, from hatching until the full yolk sac resorption (T0 to T3 at 12 °C) (mean ± SD).
thumbnail Fig. 8

Effect of temperature on the survival rate of Aquitanian pike during the first 11 weeks of life (mean ± SD).
thumbnail Fig. 9

Effect of temperature on the growth of Aquitanian pike during the first 11 weeks of life (mean ± SD).

3.4 Rearing Aquitanian pike at the aquarium of Limoges

Based on the results obtained in 2021, we decided to feed the larvae daily from 9.30 a.m. to 6.30 p.m., with Artemia nauplii only, for over a month from February 16 to March 19, 2023, with an average of 7.4 meals between March 4 to 19. Pellets were then provided alternately with Artemia from March 20 to May 27, at a rate of almost 9 meals a day. For 3 days (03/31, 04/1, 04/2), feeding pellets only was tested, but the results were inconclusive (see Denys et al., 2023). Therefore, it was decided to maintain co-feeding throughout the rearing period, which showed that it was very difficult to feed wild animals with pellets, and so the production of live prey has proved necessary to date. The trial lasted about 3.5 months, from February 16th to May 27th 2023. Larvae died during the first three weeks; no larvae died after April 24th. It should be noted that no cases of cannibalism were observed, probably due to the low density of pike per tray. Overall, 40% of the larvae (26 out of 63) survived (see Denys et al., 2023). Almost 2 years after, two fish are still present in the Aquarium.

4 Discussion

This study represents the first attempt to obtain wild eggs of Aquitanian pike directly from the field and rear them in controlled conditions. Despite the relatively low number of eggs sampled (ca. 400), we were nevertheless able to get new morphological data on both egg and larvae (Tab. 3) and to test the effects of five temperatures on the survival and growth for the first 3 months of life of this species.

Because there are neither Aquitanian pike farm nor data on the reproductive season of this species available, we had to rely on the information published on Northern pike to determine our sampling field period. According to most studies, Northern pike spawns from February to May depending on latitude (Teletchea and Teletchea, 2020). In France, Northern pike spawns mostly from February in the South to April in the North (Keith et al., 2020; Teletchea, 2020). Yet, according to our observation in the field, the first two weeks of February might be the end of the breeding period for the Aquitanian pike. Moreover, spawners in these locations were relatively small: 20–30 cm total length so with weights around 70–100 g (40 cm TL and 680 g for the longest female observed à Lit-et-Mixe in 2021) (Royer et al., 2024). So, if we estimate that the fecundity of the Aquitanian pike is the same as Northern pike (30,000 eggs/kg; Souchon, 1983), a single female isolated in a pond of both locations may do multiple spawning laying a maximum of 3 000 eggs during the breeding period. All these may explain why we were only able to collect so few eggs. However, more investigations are necessary with a specific survey in order to better characterize the breeding period of the Aquitanian pike which may be earlier than Northern pike.

Aquitanian and Northern pike possess quite similar egg and larvae (Tab. 3). The eggs are demersal, adhesive and large (Fig. 3). The egg diameter obtained here are similar to the values (2.5 to 2.9 mm) described for Northern pike females ranging from 0.3 to 4.4 kg (Bonislawska et al., 2000). Similarly, Aquitanian pike larvae resemble Northern pike larvae at hatching (see drawings in Dorier, 1938; Pospisilova et al., 2019). At hatching, larvae of Aquitanian pike measured 9.09 ± 0.24 mm (n = 14) at 12 °C, which is comprised in the range of sizes described between early hatched larvae (8.17 mm) and late hatched larvae (9.50 mm) coming from Northern pike eggs incubated as the same temperature (Trabelsi et al., 2013). The development (Tab. 1, Fig. 5) is similar to the one described for Northern pike by Dorier (1938) and for the first four weeks by Pospisilova et (al., 2019).

First feeding Northern pike larvae are usually feed either brine shrimp (Hokanson et al., 1973; Hubenova et al., 2010) or sieved zooplankton collected in ponds (Dorier, 1938; Salonen and Engström-Öst, 2013) as artificial diet is unsuitable for them (Wurtz, 1944; Hubenova et al., 2010; Imentai et al., 2024). Yet, fish farmers are interested in introducing inert items as early as possible to avoid producing live preys, which is particularly time-consuming and costly (Imentai et al., 2024). Here, we also found that Aquitanian pike were reluctant to eat inert food and fed almost exclusively on live preys during the first weeks of rearing (Figs. 6, 8 and 9). This result might also be partly due to the fact that we chose to rear the larvae in the dark during the first 7 weeks to limit stress as much as possible. Indeed, it has been shown that Northern pike larvae could feed on living active prey, even in the dark, whereas inert food was taken only in the light (Billard, 1996). Imentai et al. (2024) found that pike larvae and early juveniles grew better when fed life prey than dry diet, and that growth and survival increased with increasing light period; all larvae reared in complete darkness died during their experiment. This might also explain why the growth obtained here at 12 °C (Fig. 9) was slower during the first weeks compared to the results obtained for Northern pike (data not shown, see Denys et al., 2023). In conclusion, Aquitanian larvae should first be fed live preys for at least one week (but probably more) before starting co-feeding with inert food with at least 16 h of light (Imentai et al., 2024). At last, we observed only one case of cannibalism, which is probably due to the low density used here (Imentai et al., 2024). To limit cannibalism, Imentai et al. (2024) recommended a stocking density of 20 ind L−1 for Northern pike between 14- and 27-days post-hatching at a temperature of 20 ± 0.5 °C.

To our best knowledge, there are no snout/eye ratio values published at the larval stage comparable to those determined in juveniles and adults (Fig. 2 in Denys et al., 2014). Nevertheless, a comparison with other references was made (Dorier, 1938; Wurtz, 1944); Raat, 1988; Lancioni et al., 2005; Pospisilova et al., 2019), based on photos or scientific drawings, to calculate this ratio in Northern pike (data not shown, see Denys et al., 2023). Even though this preliminary comparison should be taken cautiously because data were obtained in different rearing conditions, it seems that already after three weeks, slight difference between the two species are apparent, and at T9, this ratio is twice greater for Northern pike than Aquitanian pike (Dorier, 1938; Lancioni et al., 2005). According to Shamardina (1957) who did the ratio between the snout length and the total length among the Northern pike, this ratio stabilizes at the T3 stage. Thus, if our result is confirmed, this could imply that these two species could be identified morphologically based on this ratio after only a few weeks post-hatching.

It is well-known that temperature strongly impacts the survival and development of early life stages of fish (Réalis-Doyelle et al., 2016, 2018, 2022). For Northern pike, several studies have tested the effects of temperature from fertilization up to hatching, known as the incubation period, and concluded that the optimal range for survival and development of embryo is probably comprised between 10 and 14 °C (Teletchea and Teletchea, 2020; Réalis-Doyelle et al., 2022), and explain why we selected 12 °C here for incubating the Aquitanian pike eggs; this was also the temperature measured on the field in 2021. As for incubation, increasing temperature strongly decreased the period from hatching until the full resorption of the yolk-sac (Fig. 7C). Besides, the survival rate was over 85% (Fig. 7A), which would confirm that Aquitanian pike larvae are as tolerant as Northern pike (Réalis-Doyelle et al., 2022). At last, larvae at the end of the yolk feeding period were similar (about 13.5 mm), except at 6 °C, where they were significantly smaller (12.3 mm) (Fig. 7B), which are comparable to the length (13–13.5 mm) obtained for Northern pike (Réalis-Doyelle et al., 2022). Then, we applied the same five temperatures up to three months after hatching to evaluate the possible effects for such a long period, which has never been tested on Northern pike, i.e., only up to four weeks (Hokanson et al., 1973). After 28 days post-hatching (T4), Aquitania pike were much smaller than Northern pike for the three tested temperatures in common between the two studies: 14 vs 25 mm (at 12 °C), 14 vs 34 mm (at 15 °C) and 15 vs 42 mm (at 18 °C) (Hokanson et al., 1973). This slower growth might be due to the fact that we reared larvae in total obscurity up to T7 and that we had to anesthetize them regularly (ca. once every two weeks) to follow growth. Besides, for Northern pike, larvae longer than 30 mm were fed an excess ration of yolk-sac larvae to minimize cannibalism and insure good growth or larger individuals (Hokanson et al., 1973). At the end of the three months (T11), the better results in term of survival (Fig. 8) were obtained at 12 °C (60%) and for growth (Fig. 9) at 15 °C (34.11 mm), followed at 12 °C (27.85 mm). Given the low number of larvae tested per temperature (Tab. 2), those results should be considered preliminary, but is seems that the optimal temperature of Aquitanian pike larvae is comprised between 12 and 15 °C.

Based on these results, we were able to rear Aquitanian pike in the Aquarium of Limoges in 2023 and then present two individuals for more than 2 years in order to promote the conservation of this species to the public, illustrating the potential of collaborations between angling federations, public aquariums and academic research for both research and conservation of fish (Teletchea et al., 2023).

Acknowledgments

This work was supported by the Lorraine University, the Muséum national d’Histoire naturelle (MNHN), the UAR PatriNat 2006, the UMR BOREA 8067 and the Union of Angling Federations of the Adour-Garonne Basin (UFBAG). This study is included within a global project about the Aquitanian pike BIOESOX funded by the UFBAG and the French Federation of Angling in France (FNPF). We thank also the hunting federations to give us access to the breeding sites, P. Antonetti (MNHN) who identified the aquatic plants, as well as L. Jamet (Sorbonne Université) who helped us to collect eggs on the field.

Supplementary materials

Fig. S1. Cannibalism observed among larvae at 12 °C on March 25, 2021 (46 days after hatching). Predator = 17.18 mm; Prey = 13.25 mm.

The Fig. S1 is available at https://doi.org/10.1051/kmae/2025030/olm

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Cite this article as: Teletchea F, Rech G, Royer L, Escarpit M, Renard V, Chardard D, Spadiliero F, Branthome D, Hautecœur M, L’Hostis A, Denys GPJ. 2026. Early life stages of Aquitanian pike Esox aquitanicus (Teleostei, Esocidae): first description of morphological development and trials of rearing in a freshwater reservoir. Knowl. Manag. Aquat. Ecosyst., 427, 1. https://doi.org/10.1051/kmae/2025030

All Tables

Table 1

Morphological development of the Aquitanian pike during the first 11 weeks post-hatching when reared at 12 °C (n = 15 larvae; reared individually in a petri dish), see Figure 5.

In the text
Table 2

Initial number of larvae per temperature tested, and per tray.

In the text
Table 3

Comparison of early life stages of Aquitanian common pikes. Data for common pike were taken from Teletchea et al. (2007), completed with those on-line here https://www.storefish.org/species/esox-lucius). Definitions of traits can be found here https://storefish.org/description.

In the text

All Figures

thumbnail Fig. 1

Distribution area of the two pike species in France (Esox aquitanicus in red, Esox lucius in its native area in blue and introduced in green) (modified and adapted from Keith et al., 2020; Royer et al., 2024), with the sampling locations of Aquitanian pikes breeding areas in the Courant de Contis watershed (Landes department; southwestern France): the Plaine aux Pigeons at Lit-et-Mixe and the marsh of Uza; credits photos: G. Denys.
In the text
thumbnail 2

Snout length (SnL) versus horizontal eye diameter (EyD). Drawing by Guillaume Rech.
In the text
thumbnail Fig. 3

Egg of Aquitanian pike (from batch 1, photographs taken on February 6th, 2021). Egg diameter = 2.83 mm. Scale = 1 mm.
In the text
thumbnail Fig. 4

Larvae at hatching of the Aquitanian pike larvae (batch 2, from February 19, 2021). TL = 9.24 mm. Scale = 1 mm.
In the text
thumbnail Fig. 5

Morphological development of the Aquitanian pike during the first 11 weeks post-hatching (n = 15 larvae; reared individually in a petri dish) at 12 °C, see Table 1. Drawing by Guillaume Rech. Scale = 1 mm.
In the text
thumbnail Fig. 6

Evolution of the ratio of snout length compared to the eye diameter during 11 weeks at 12 °C (mean ± SD).
In the text
thumbnail 7

Effect of temperature on the survival rate (A), larval size (B), duration (C) and daily growth (D) during the endogenous feeding period, i.e, from hatching until the full yolk sac resorption (T0 to T3 at 12 °C) (mean ± SD).
In the text
thumbnail Fig. 8

Effect of temperature on the survival rate of Aquitanian pike during the first 11 weeks of life (mean ± SD).
In the text
thumbnail Fig. 9

Effect of temperature on the growth of Aquitanian pike during the first 11 weeks of life (mean ± SD).
In the text

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