Karthik Masagounder (Ph.D.)


“Improving rearing efficiency of large bluegill by reducing social costs and enhancing feed quality”


Advisor: Dr. Robert S. Hayward


Existing culture technology for bluegills (Lepomis macrochirus)  requires more than two years of pond rearing to produce them within the prevailing food-market size range of 227-340 g, which seems to be less or no profitable to fish producers in the Midwest U.S. Recent work at MU demonstrated that male bluegills have substantially greater growth capacity than females when they were reared in isolated chambers. However, predominantly male bluegill groups did not differ from mixed sex groups in growth performance when reared in indoor system. It was recently identified that formation of social hierarchy enabled only fewer dominant fish increasing access to feed which eventually caused poor feed and growth efficiency, both in mixed-sex and predominantly-male groups. My work will involve ameliorating adverse social interactions among bluegills and thereby allowing them to grow at rates closer to their inherent capacity in indoor rearing systems. I try to accomplish this goal by evaluating

          (i) the effects of physical structures on growth and social hierarchy of juvenile bluegills - an approach via reducing visual encounters

(ii) the effectiveness of a “topping-off” approach to increase production of food-size bluegills via sequential removal of dominant fish

Unlike indoor system where bluegills are grown under high rearing density and with artificial feed, pond system provides natural shelters, and natural feed, which may wane the interference competition. It may be possible that prolonged rearing allows establishment social hierarchy and impedes inherent growth capacity. My objective is to evaluate potential to grow higher number of bluegills to food-market size more readily in ponds, by rearing predominantly male bluegill groups and reducing social costs, if present.

Whilst social costs impeding the rearing efficiency, excess fat accumulation have been observed in the visceral organs at least for the dominant bluegills in the group. It was identified that farmers, because of absence of specific feed, use other commercial diets such as those developed for trout and catfish. Feeding bluegills with non-specific diets led to problems such as increased feed cost and fat deposition. Social hierarchy and non-specific feed (eg. trout feed), together, questioned the profitability and long term survivability of the farming because of the increased operational costs. My goal in this part is to develop a suitable practical diet for juvenile and adult bluegills by optimizing amino acid and energy requirements. This study will involve determining

          (i) apparent digestibility values of common feedstuffs for bluegill using individual test ingredients

          (ii) lysine and other Essential Amino Acid (EAA) requirements for juvenile and adult bluegills

          (iii) optimum protein and energy levels in the diet for juvenile and adult bluegills




Masagounder, K., J. Firman, R. S. Hayward, P. Brown, S. Sun (2007). Determination of Apparent Digestibility of Common Feedstuffs for Bluegill, Lepomis macrochirus and Largemouth bass, Micropterus salmoides using individual Test Ingredients, Aquaculture Nutrition (under revision)


Karthik, M., J. Suri, N. Saharan, and R.S. Biradar, 2005. Brackish water aquaculture site selection in Palgar Taluk, Thane district of Maharashtra, India, using the techniques of Remote Sensing and GIS, Aquacultural Engineering, 32(2): 285-302


Karthik, M., D. B. Akolkar, V. Kumar, and S. D. Singh, 2006. Genetically modified fish and its potential applications. Aquaculture Asia Magazine, 6(2): 13-18 (popular article)


* Karthik, M is later changed to Masagounder, K!




(Invited presentation) Hayward, R. S., and K. Masagounder. 2007.  Examination of two impediments to beneficial use of compensatory growth in aquaculture.  In  Symposium titled: Physiological Insights Towards Improving Fish Culture.  Aquaculture 2007, February 26-March 2, San Antonio, Texas.


Hayward, R. S., K. Masagounder, and A. J. Doerhoff. 2007.  Developing capacity to rear large sunfish efficiently. Mid-continent Warm-water Fish Culture Conference, February 5-7, Kansas City, Kansas.


Masagounder, K., and Hayward, R. S., 2006. Evaluation of a compensatory growth feeding regime for bluegills in recirculating aquaculture systems. In  Symposium titled: Sunfish and Black bass culture: an update on progress.  Aquaculture 2006, February 13-16, Las Vegas, Nevada.