Technical contribution Length–weight relationships and reproductive parameters of Amblyceps apangi Nath and Dey, 1989 from Nagaland, India By L. N. Humtsoe and S. Bordoloi Resource Management and Environment Section, Institute of Advanced Study in Science and Technology, Guwahati, Assam, India Summary The present study describes certain biological parameters of a hill stream catfish, Amblyceps apangi Nath and Dey, 1989 first described from Arunachal Pradesh, India. The distribu- tional range of the fish was later recorded from the states of Manipur and Nagaland. The fish is very rare and this is the first report on certain biological parameters based on collec- tions (140 males, 105 females) from streams in the Doyang watershed, a tributary of the Brahmaputra River. The value of the allometric coefficient (b) indicated close to isometric growth in males (2.989) and negative allometric growth in females (2.945). The relative condition factor was found to be close to 1 in different size groups. Both males and females attained first maturity (M 50 ) in length group 6.0–7.0 cm. Peak values (Male 0.424, Female 1.465) in the gonadosomat- ic index (GSI) occurred from April to May, indicating one spawning season per year. The overall female to male ratio was 1 : 1.33. Absolute fecundity ranged from 17 to 122 for fishes of total length 6.34–10.3 cm. Introduction Amblyceps apangi Nath and Dey, 1989 was first described from Arunachal Pradesh, India. This Silurid catfish belongs to the family Amblycipitidae that inhabit highly torrential streams and is extremely rare (‘Vulnerable’ as per CAMP, 1998). The fish was later reported from Manipur (Vishw- anath and Linthiongambi, 2007) and Nagaland (Humtsoe and Bordoloi, 2009). This is the first report on certain bio- logical parameters based on collections (140 males, 105 females) from streams of the Doyang watershed, a tributary of the Brahmaputra River. The present study provides information on the sex ratio, length-weight relationships, relative condition factor (Kn), size at first maturity, gonadosomatic index, sex ratio and fecundity of A. apangi, based on collections from Nagaland during 2005–2007. Materials and methods Between 2005 and 2007, a total of 245 Amblyceps apangi speci- mens were collected whenever sighted from one of the seven hill streams in Wokha district (25°55 0 –26°35 0 N and 94°10 0 – 94°25 0 E), namely, Nhyatsutchu, Kyotchu, Nitsutchu, Humtso Tsupvu, Sosurotchu, Vekhvurotchu and Yikhum Sanga, all of which flow into the Doyang River, an important tributary of the Brahmaputra River in Assam. The fishes inhabit highly torrential streams and die as soon as they are removed from water. The collected specimens were preserved in 6% formal- dehyde solution and measurements taken and retained for fur- ther laboratory study. Measurements were made with vernier caliper to the nearest 0.01 cm. Body weight was taken nearest to 0.01 g with a digital balance. Sexes were determined by dis- secting the specimens. The length-weight relationship was cal- culated by using the formula, W = aL b (Le Cren, 1951; Froese, 2006), where W is the fish weight (in g), L is the total length (in cm), ‘a’ is the co-efficient related to body form and ‘b’ is an exponent indicating isometric growth when equal to ‘3’. The values of ‘a’ and ‘b’ were calculated by linear regres- sion with log transformed data Log W = Log a + Log b L. The relative condition factor (Kn) was determined after Le Cren (1951) following the equation Kn = W/W 1 , where W = weight of fish observed and W 1 = calculated weight as determined from the length-weight equations. The sex ratio was calculated for males and females col- lected throughout the different seasons. The data presented does not portray the actual sex ratio, as this was calculated only from available collections. The average size of the fish at first maturity (M 50 ), which is the length at which 50% of the fishes are at an advanced stage of the first sexual cycle (at least Stage-III of the maturity cycle, as suggested by Tweddle and Turner, 1977), was determined by calculating the percentage of the number of mature males and females to the total number of fishes examined in a particular length group during the spawning season. GSI value was calculated based on the formula suggested by Vladykov (1956) and Lagler (1971), which is expressed as: GSI = Weight of gonads 9 100/Body weight. Absolute fecundity was determined from 20 fully matured female fishes. The ovaries were removed and dissected, and the length and weight recorded and preserved in 4% forma- lin solution. Mature ova from both parts of the ovary were then spread on a glass slide and counted with the help of a binocular microscope. The relationship between fecundity (F) J. Appl. Ichthyol. (2015), 1–3 © 2015 Blackwell Verlag GmbH ISSN 0175–8659 Received: April 24, 2014 Accepted: January 30, 2015 doi: 10.1111/jai.12827 Applied Ichthyology Journal of