Rearing Male Bluegills Indoors May Be Advantageous for Producing Food‐size Sunfish

Abstract

Abstract.— An indicated demand for sunfish (Lepomis spp.) as a food fish remains untested because of continuing inability to efficiently rear these fishes to required large sizes (≥227 g; 0.5 lbs). A recent study involving parallel, indoor rearing of two sunfishes under favorable conditions showed that bluegills Lepomis macrochirus possessed markedly higher growth capacity than B × G hybrids (F1: male bluegill × female green sunfish, Lepomis cyanellus). B × G hybrids had been thought to possess superior growth capacity and so have received more attention than bluegills as a food‐fish candidate in many areas of the USA. Reanalysis of data from the recent study with emphasis on gender differences revealed that the male bluegills possessed much higher growth capacity than male B × G hybrids, at least from May to March as Age 1 and then early Age 2 fish. Male bluegills reached 67% of food‐market weight within the 10‐mo period from a starting weight of 7 g; male B × G hybrids reached only 24% of this weight. Male bluegills’ more rapid growth versus male B × G hybrids’ apparently involved less growth energy allocation to gonad development. Female bluegills grew slower than male bluegills but also outgrew male and female B × G hybrids whose growth trajectories declined in midsummer (June) and remained largely flat through March. The previous view that B × G hybrids possess higher growth capacity than bluegills was fostered by studies in ponds where bluegill growth can be impeded by high reproduction rates and, as this study reveals, by high densities and exposure to suboptimal temperatures when their growth potential is high. Indoor rearing of male bluegills should ameliorate most pond‐related growth impediments and take fuller advantage of their rapid growth capacity.

Establishment of Mostly Male Groups of Bluegills by Grading Selection and Evaluation of their Growth Performance

“…There was also a significant difference detected in slopes of the linear regressions between the top 25% treatment and mixed control groups. These results indicate that communally reared male bluegills are able to grow faster than mixed-sex or female bluegill populations in regular aquaculture settings and that the social interaction costs that can impede the growth of grouped male bluegills (Hayward and Wang 2006) were not high enough to override the males' higher growth capacity. However, it appears that the top 25% and top 50% treatments exhibited superior growth during weeks 8-32 of the culture period but relatively inferior growth during the latter part of experiment.…”

“…The capacity to form mostly male bluegill groups has the potential to increase bluegill production efficiency and the ability to rear large bluegills, which are in demand as food fish (Hayward and Wang 2006) and command high prices (R. Butz, Windridge Farm, Germantown, Maryland, personal communication). Producers can consider culturing larger fish for food markets and holding or rearing small-to intermediate-sized fish for recreational fishery stocking.…”

“…Male bluegills appear to hold the greatest potential for the food market due to their more rapid growth capacity relative to that of females (Hayward and Wang 2006). Male bluegills outweighed female bluegills by 111.9% at the end of a 300-d experiment and were also significantly larger than both male and female hybrid bluegills that were reared in parallel (Hayward and Wang 2006).…”

Comparison of dietary essential amino acid requirements determined from group-housed versus individually-housed juvenile bluegill, Lepomis macrochirus

“…Bluegill, Lepomis macrochirus , once considered an emerging aquaculture species in the United States (Morris & Mischke 2003), now appears to be moving towards larger‐scale production because of increased interest in this species as a food fish, coupled with evidence that it, and related hybrids, can be efficiently grown to food size through selective breeding (Hayward & Wang 2006; Hicks et al. 2009).…”

A first genetic linkage map of bluegill sunfish (Lepomis macrochirus) using AFLP markers

“…The prolific nature and precocious maturation of the bluegill have long been recognized as the cause of over-crowding and stunting in culture situations. One recent study showed that bluegill males grow twice as fast as females (Hayward and Wang 2006). Consequently, much interest has been generated concerning the development of monosex male populations and fast-growing strains through selective breeding.…”