Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Short communication The applicability of large-scale sperm cryopreservation in wels catfish (Silurus glanis) optimized for hatchery practice Zoltán Bokor a,1 , Gergely Bernáth a, ⁎ ,1 , Levente Várkonyi a , József Molnár a , Zete Levente Láng a , Zsófia Tarnai-Király a , Enikő Solymosi b , Béla Urbányi a a Department of Aquaculture, Szent István University, 1 Páter Károly Str., H-2100 Gödöllő, Hungary b Szegedfish Ltd., 2 Nádvágó Str., H-6728 Szeged, Hungary ARTICLE INFO Keywords: Wels catfish Large-scale Cryopreservation Motility assessment Sperm ABSTRACT In the presented study, effects of sperm cryopreservation methods (Polystyrene box-P. box vs a controlled-rate freezer-CRF) and various semen confection methods during freezing (5 mL straw vs. 10 mL cryotube) on sperm motility parameters and fertilization capacity of wels catfish (Silurus glanis) were tested. In general, pMOT (Control: 89 ± 3%, Straw P. box: 50 ± 9%, Straw CRF: 53 ± 12%, Cryotube: 52 ± 7%) and BCF (Control: 30 ± 1 Hz, Straw P. box: 27 ± 1 Hz, Straw CRF: 26 ± 1 Hz, Cryotube: 27 ± 1 Hz) showed significant re- duction following thawing. ALH reduced significantly in the case of the straw frozen with P. box (1.2 ± 0.2 μm) compared to the fresh control (1.5 ± 0.1 μm). However, VCL (Control: 108 ± 6 μm/s, Straw P. box: 107 ± 5 μm/s, Straw CRF: 108 ± 8 μm/s, Cryotube: 109 ± 7 μm/s) and VSL (Control: 94 ± 6 μm/s, Straw P. box: 99 ± 4 μm/s, Straw CRF: 99 ± 9 μm/s, Cryotube: 99 ± 7 μm/s) did not decrease. A significantly higher LIN was measured using the straw cryopreserved in the P. box (92 ± 2%) and the CRF (91 ± 2%) in com- parison with the fresh control (86 ± 1%). No significant difference in the fertilization capacity when eggs were fertilized by frozen/thawed (Straw P. box: 75 ± 5%, Straw CRF: 72 ± 3%, Cryotube: 66 ± 6%) or fresh (control, 68 ± 4%) semen was observed (P > .05). As well, no significant correlation between none of sperm motility parameters tested and the fertilization rate were recorded (P > .05). All tested sperm cryopreservation showed a similar high efficiency in the hatchery practice of wels catfis. 1. Introduction Cryopreservation allows long-term storage of fish sperm for even several years at permanent quality (Bernáth et al., 2017). Different freshwater and marine fish species-specific protocols were developed a few decades ago. One of the main purposes for the development of freezing protocols is to assist the aquaculture production (Martínez- Páramo et al., 2017). The investigation of different factors (cooling rate, composition of the extender, cooling equipment, type of the cryopro- tectant etc.) affecting the survival rate of spermatozoa following thawing has an important role in the development of protocols. Fur- thermore, the optimization and improvement of large-scale sperm cryopreservation can support the successful adaptation of different freezing methods to the hatchery practice (Hu et al., 2014; Várkonyi et al., 2018). Wels catfish (Silurus glanis) is an economically important predator fish species in Europe (Linhart et al., 2005). The species was defined as a remarkable gamefish as well (Copp et al., 2009). Although, the pro- pagation of wels catfish has already been developed, the common hatchery practice faces several difficulties (Bokor et al., 2010). The regular abdominal stripping method of males can result in varying sperm quantity and quality. Dissection and squeezing of testis was common in hatchery practice to obtain a higher quality and enough quantity of sperm. However, males were killed during the propagation process which implies direct economic loss to the fish farms (Bokor et al., 2010; Ogier de Baulny et al., 1999). Sperm cryopreservation can support the hatchery protocols with optimized sperm utilization during propagation. The development of freezing protocols started over 20 years ago (Bokor et al., 2010) however, the established methods were mainly suitable only for experimental conditions (Linhart et al., 1993, Ogier de Baulny et al., 1999 etc.). Bokor et al. (2010) and Linhart et al. (2005) were already able to freeze an increased amount of catfish sperm (volume 1–5 mL) successfully. However, limited information is available regarding the application of large-scale cryopreserved catfish https://doi.org/10.1016/j.aquaculture.2019.03.064 Received 28 January 2019; Received in revised form 12 March 2019; Accepted 27 March 2019 ⁎ Corresponding author. E-mail address: Bernath.Gergely@mkk.szie.hu (G. Bernáth). 1 These authors contributed equally to this work. Aquaculture 506 (2019) 337–340 Available online 28 March 2019 0044-8486/ © 2019 Elsevier B.V. All rights reserved. T