Introduction
The pikeperch (Sander lucioperca) is a commercially important species in Europe, with well-established protocols of artificial reproduction. However, these protocols are labor-intensive and often require repeated handling of broodstock females, which can induce acute stress and increase broodstock mortality (Rónyai, 2007,) what can even potentially negatively affect offspring quality (Rasal et al., 2024). The largemouth bass ( Micropterus salmoides ) is primarily significant in Europe for recreational angling. However, its low-fat flesh and high-quality fillet have made it globally popular among health-conscious consumers (Parmar et al., 2022). At the same time, rising expectations regarding product quality have led to a decline in demand for common carp (Cyprinus carpio) (Hu et al., 2023), resulting in China’s annual production of largemouth bass for human consumption approaching one million tons (Liu et al., 2022). However, most of the production is seasonal and/or based on nest spawning technology , which may involve limited controllability and low biological diversity. Despite the high production volume, no well-developed artificial reproduction protocol has been published to date, while the precise spawning ethology of the species remains undescribed. Given these challenges, the objective of the present study was to describe the spawning indicators in both species through camera observation and recording.
Materials and methods
In January 2025, during preseason pikeperch reproduction, six pairs of breeders were hormonally stimulated with salmon gonadoliberin analog using the warming thermal regime (Ljubobratović et al., 2021) . The 6 pairs of breeders were placed in two 4m3 tanks , divided into three spawning chambers , creating a total of six bree ding units . In each unit, an artificial nest was placed, made of artificial grass , and an underwater lighting system , programmed to a 12:12 LD photoperiod, with a camera above each compartment. After spawning, nests containing fertilized eggs were placed individually into conical incubators for incubation, and the hatched larvae were subsequently counted. In April 2025, six pairs of largemouth bass breeders were placed into three s pawning tanks, each tank with two pairs, with three different setups: D - divided tank : the tank separated in the middle by a partition net, one nest per pair of breeder; CH - ch ambered nest tank: first and last third the tank each with a nest at in the cover with an empty third in the middle and securing free movement throughout the tank and hiding are for females; F – free tank : one nest at each end of the tank , securing free movement throughout the tank without any chambers included. Fish were hormonally stimulated with human chorionic gonadotropin three days upon stocking, and t he behavior of the fish was further camera-monitored. After spawning, eggs were collected from the nests , their number and embryo survival were evaluated, and stocked in Zug jars for incubation.
Results
During the pike-perch spawning experiment, spawning was observed in all six pairs on the 8th and 9th days after hormonal stimulation . After placing the artificial nests into the incubators, the number of hatched larvae was assessed and ranged from 15.200 to 28.899.. In the case of the largemouth bass experiment, a mong three setups, the tank equipped with half partitions proved to be the most effective. Two nests contained eggs, and CH treatment yielded ~80 thousand live eggs while the F nest contained close to 40 thousand live eggs. The hatching rate was 100% for both nests. B oth at the beginning and the end of the experiment, the males were spermiating.
Discussion
Artificial intelligence is increasingly gaining ground in various areas of aquaculture and has already been successfully applied in several production processes, such as feeding management and health monitoring (Mandal & Ghosh, 2024). Animal welfare is also receiving growing attention, particularly in relation to behavior-based indicators, which have recently come into focus (Barreto et al., 2022). By utilizing spawning indicators based on video monitoring, new protocols can be developed that not only improve the survival rate of broodstock but may also positively affect the quality of eggs and larvae. Previous research has shown that problems affecting the parents can have molecular-level effects on their offspring, influencing their later performance (Rasal et al., 2024). The present research led to the description of the ovulation indicators that will be further utilized to set the new spawning protocol, reducing the fish handling and labor requirements.
Acknowledgements
This work was supported by the Research Excellence Programme and by the Flagship Research Groups Programme of the Hungarian University of Agriculture and Life Sciences.
Reference
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