Effect of a light change in conical lift nets on the length and weight composition of Common sprat (Clupeonella caspia, Svetovidov, 1941) from Amirabad fishing port

The research study the effect of changing light color on the length and weight composition of common sprat (C. caspia) catch in conical lift net with a mesh size of 8 mm (knot to knot). For this purpose, in January 2018 the sprat fish caught by three fishing vessels during 30 times of fishing operations at 50-40 m depth in Amirabad fishing port. The results showed that from total number of 2874 caught, C. caspia with 79% was the most catch and C. engrauliformis and C. grimmi with 14% and 7% of the catch, respectively. Fish caught in blue light had a larger length range and more weight. While the fish caught in red light had the lowest length range and the lowest weight. In blue and red light, the highest and lowest average length and weight of C. caspia was 11.59 cm, 11.00 cm, 11.47 grams, and 11.00 grams, respectively. The length and weight of C. caspia caught in white light was intermediate.  The average length and weight of C. caspia caught using blue and red color, and white and red color had a significant difference (p<0.05).