Summary The objective of this work was to evaluate the sperm motility of 13 Steindachneridion parahybae males using open‐source software (ImageJ/CASA plugin). The sperm activation procedure and image capture were initiated after semen collection. Four experimental phases were defined from the videos captured of each male as follows: (i) standardization of a dialogue box generated by the CASA plugin within ImageJ; (ii) frame numbers used to perform the analysis; (iii) post‐activation motility between 10 and 20 s with analysis at each 1 s; and (iv) post‐activation motility between 10 and 50 s with analysis at each 10 s. The settings used in the CASA dialogue box were satisfactory, and the results were consistent. These analyses should be performed using 50 frames immediately after sperm activation because spermatozoa quickly lose their vigor. At 10 s post‐activation, 89.1% motile sperm was observed with 107.2 μm s−1 curvilinear velocity, 83.6 μm s−1 average path velocity, 77.1 μm s−1 straight line velocity; 91.6% were of straightness and 77.1% of wobble. The CASA plugin within ImageJ can be applied in sperm analysis of the study species by using the established settings.

Summary The objective of this study was to assess the effect of storage temperature on the fresh sperm quality of Steindachneridion parahybae over 112 h of storage. Semen collected from five males was tested in a 12 × 4 factorial experimental design using the sperm storage times of: 0 (control), 1, 2, 4, 8, 16, 24, 36, 48, 64, 88, and 112 h after collection. Temperatures tested were (mean ± SD): 5.2 ± 3.4, 12.9 ± 1.6, 24.4 ± 1.7 and 34.9 ± 1.1°C. Sperm parameters were motility rate (MOT), curvilinear velocity (VCL), average path velocity (VAP), straight line velocity (VSL), straightness (STR), sperm normality (NOR) and survival rate (SUR). The parameters VCL, VAP and VSL were grouped by principal component analysis to create the sperm velocity (VS). The parameters assessed exhibited effects (P < 0.05) of the exposure time and temperature. Interactive effects between temperature and time (P < 0.05) were observed for STR, NOR and SUR, and quadratic effects for factors MOT and VS (P < 0.05). Pearson's linear correlation was verified between the parameters studied (P < 0.05), indicating MOT, VCL and STR as good indicators of sperm quality. Chilling at temperatures around 5°C and heating at around 35°C were harmful to S. parahybae spermatozoa. It is suggested that short‐term (up to 8 h) semen storage – if necessary – should be within a range of 15–25°C.

Steindachneridion parahybae is an endemic catfish to the Paraiba do Sul river basin classified as critically endangered. Little is known about the reproductive management of this species in captivity, adopting for this practice empirical measures. The objectives were to:(1) determine suitable Accumulated Thermal Units (ATUs) at the moment of ovulation in January 2011 and 2012; (2) follow initial larvae rearing in 180, 240 and 300 degreehours. Nine selected females were divided into three experimental groups of three specimens each (replications), distributed at pre-established times: 140, 160, 180, 200, 220, 240, 260, 280 and 300 degree-hours. The females were induced with two doses of 0.5 and 5.0 mg kg -1 of dry carp pituitary, respectively, at an interval of 12 h. The extruded oocytes were kept at average water temperature of 22.35 ± 0.53°C (2011) and 21.88 ± 0.15°C (2012). Fertilization and hatching rates were: 84.22 and 71.33 % at 174.2 ATUs in 2011, and 55.58 % and 36.13 % at 251.0 ATUs in 2012. In January 2012, 900 larvae were distributed in three replications (triplicate) consisting of 100 larvae each and were fed: 120 (second day), 300 (thirdfourth day), 600 (fifth-eighth day), and 1,200 Artemia salina nauplii per larva (ninth-15th day), six times a day. The larvae exhibited mean weight of 523.67 ± 54.42, 496.67 ± 61.98 and 475.00 ± 22.83 mg, length of 17.75 ± 0.57, 17.58 ± 0.51 and 17.45 ± 0.25 cm and survival of 63.95 ± 24.50, 71.71 ± 6.61 and 79.65 ± 0.82 %, when hatched in 180, 240 and 300 ATUs, respectively. The larvae body parameters did not show significant differences at these degree-hours.

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The Steindachneridion parahybae is an endangered catfish from Brazil and strategies applied for gametes optimization are necessary. The aim of this study was to assess inseminating doses and water volume upon the fertilization, hatching rates and percentage of normal larvae in S. parahybae. Was used a randomized design in factorial scheme (4×4) with four inseminating doses: 1.0×10 4 , 1.0×10 5 , 1.0×10 6 , 1.0×10 7 spermatozoa oocyte -1 and four volumes of water: 1, 35, 65 and 95mL of water g -1 of oocytes. The combination of doses and volumes were performed in triplicates (n=48). Each incubator (1.5L of useful volume) with 1g of oocytes was considered as an experimental unit. Significant interaction between inseminating doses and volumes of water to the values of the fertilization rates and quadratic effect of doses and volume for the values of hatching rates were observed. The doses and volumes did not influence the percentage of normal larvae (87.70±5.06%). It is recommended the use of 5.5×10 6 spermatozoa oocyte -1 and 1mL of water g -1 of oocytes during in vitro fertilization procedure. These results allowed us to develop new biotechnological strategies applied to the conservation of S. parahybae.O Steindachneridion parahybae é um bagre ameaçado de extinção no Brasil e estratégias aplicadas para a otimização de gametas são necessárias. O objetivo deste estudo foi avaliar doses inseminantes e volume de água sobre os valores das taxas de fertilização, eclosão e larvas normais em S. parahybae. Utilizando-se um delineamento experimental casualizado em esquema fatorial (4×4), com quatro doses inseminantes: 1,0×10 4 ; 1,0×10 5 ; 1,0×10 6 ; 1,0×10 7 espermatozóides ovócito -1 e quatro volumes de água: 1; 35; 65 e 95mL de água g -1 de ovócitos. As combinações de doses e volumes foram realizadas em triplicatas (n=48). Cada incubadora (1,5L de volume útil) contendo 1g de ovócitos foi considerada como uma unidade experimental. Interações significativas entre doses inseminantes e volumes de água para os valores das taxas de fertilização e efeito quadrático das doses e do volume para os valores das taxas de eclosão foram verificadas. As dosagens e os volumes aplicados não influenciaram no percentual de larvas normais (87,70±5,06). Recomenda-se a aplicação de 5,5×10 6 espermatozoides ovócito -1 e a utilização de 1mL de água.g -1 de ovócitos no procedimento de fertilização artificial in vitro. Estes resultados permitiram desenvolver novas estratégias biotecnológicas aplicadas na conservação do S. parahybae.