is not permanent, it is expected that the trait might have some survivability trade-offs in the absence of predators. Notably, the deep-bodied morph is associated with compromised immune function and resource allocation. Specifically, deep-bodied crucian carp have a lower level of baseline natural antibodies relative to the sleeker-bodied morphs. In addition, crucian carp with the deep-bodied morphology exhibit reduced growth rates when compared to their sleeker-bodied counterparts. Physiology Carassius species exhibit some remarkable physiological adaptations to their environment. For example, in entirely anoxic conditions during winter Carassius carassius can survive for considerable periods by anaerobic respiration, with ethanol as the major metabolic end product; a facility that is highly unusual among vertebrates. During summer the fish also may survive anaerobic conditions by this metabolic expedient, though only to a far more limited extent; the winter phenotype can sustain fermentation as a substitute for respiration for several weeks on end. Experimentally the fish have been maintained under anoxic conditions for 140 days. Anoxia can be tolerated longest in the coldest water, even down to 0 °C, because colder conditions lower the metabolic rate. Alcohol production occurs mainly in the muscle tissues, but also in the liver, where the process is thought to have originated. Similarly goldfish can produce alcohol in muscle tissues, but to a much more limited extent. Experimentally it has been demonstrated that the metabolic process involves the production of pyruvate from lactate, followed by decarboxylation to acetaldehyde which then is hydrogenated to ethanol as the major metabolic end product. In turn the fish largely excretes the ethanol into the water rather than accumulating it to toxic levels in the tissues. Excretion of lactate in significant quantities is not a common nor a desirable metabolic facility, but the excretion of ethanol presents no serious metabolic challenges. This metabolic expedient avoids the fatal accumulation of acid end-products of anaerobic glycolysis. Sport fishing In Britain, leisurely or competitive catching of this fish by rod and tackle belong in the coarse fishing category. The British rod-caught record for largest crucian is four pounds, nine ounces, (2.085 kg) landed by Martin Bowler in 2003, tied by Joshua Blavins in 2011. There have been various bids for a breakage of this record since, but they were rejected as not "true" crucians" but rather, e.g. a "brown goldfish variant" (i.e., hybrid born between the non-native goldfish or gibelo species and the British crucian). In the