Black color occurs in coloration of many freshwater fish beening relatively constant throughout the year and cryptic (in such, for example, bottom dwelling fish as wels, Silurus glanis). In this paper, we will consider those frequent cases when chiefly males of freshwater fish acquire black coloration in the reproductive period (nuptial melanization).

For desalinated areas and rivers of the Ponto-Caspian basin, five species of gobiid fish with nuptial melanization of body are most typical and abundant. Round goby, Neogobius melanostomus, monkey goby, N. fluviatilis, ratan goby, N. ratan, black goby, Gobius niger, and racer goby, Mesogobius gymnotrachelus, are among them. Gobies are marine origin, but the foregoing species (as well as many amelanistic species) inhabit desalinated areas and readily migrate into rivers of the Ponto-Caspian basin where successfully breed (Pinchuk et al., 1985; Romanesku, 2012). Some other euhaline gobies develop black nuptial coloration, such as giant goby, Gobius cobitis), but they avoid oligohaline bays and fresh waters.

In the reproductive period, gobies acquire conspicuous black coloration practically of the whole body using such an appearance, on the one hand, to repel rivals (in this case, black coloration is called threat, or antaposematic) and, on the other hand, to attract females (Trifonov, 1955; Yankovsky, 1966). Some gobies acquire color rims on the edge of both dorsal fins, pair pectoral and anal fins: white in N. melanostomus, yellow in M. gymnotrachelus and orange in N. fluviatilis. In accordance with the accepted terminology (Trifonov, 1955; Yankovsky, 1966), these conspicuous color signs are called gamosematic, bacause these signs appear in males when they prepare the nests, indicating in this way on their readyness to breed, and disappear in males when they begin to protect the nests with laying eggs.

Spawning and nest guarding in N. melanostomus are well documented (Meunier et al., 2009).

In general, round goby, N. melanostomus, and other gobies are rather visually guided fish with the specialized chemoreceptory channel. N. melanostomus respond poorly to the odors of lake whitefish (Coregonus) tissues, crushed dreissenids and fish eggs (Sreedharan et al., 2009; Yavno & Corkum, 2011). At least Sreedharan et al. (2009) do not recommend to use food-baited traps to control the spread of these fish. According to Rollo et al. (2007), N. melanostomus have well developed vocalization and are attracted by conspecific calls in both laboratory and field trials.

Nuptial melanization is also found in such fish of the North American ichthyofauna as dirty darter, Etheostoma olivaceum, Gila topminnow, Poeciliopsis occidentalis, and Olympic mudminnow, Novumbra hubsi (Kodric-Brown, 1998). Coloration of males in brook stickleback, Culaea inconstans (Ward & McLennan, 2006), mosquitofish, Gambusia holbrooki (Horth, 2004) and Amur sleeper, Percottus glehni (Tsepkin, 1977), are other examples of nuptial melanization.

Interestingly, in mosquitofish, G. holbrooki, black males have advantages and disadvantages to more common silver rivals. On the one hand, largemouth bass, Micropterus salmoides, crayfish (Procambarus) and dragonfly larvae (Libellulidae) prefer, as natural predators, silver males (Horth, 2004), that is black males are under less predation pressure. According to Taylor et al. (1996), on the other hand, females of G. holbrooki prefer silver males and even can avoid black males.

Basic References

Horth L. 2004. Predation and the persistence of melanic male mosquitofish (Gambusia holbrooki). Journal of Evolutionary Biology 17, 672-675

Kodric-Brown A. 1998. Sexual dichromati ... Read more »

Conspicuous coloration of males occurs in many species of fish, birds and other animals being advantageous in attracting potential mates. Although bright colors can entice females of the same species, these colors may also attract predators. Female choice for bright males and an enhanced risk of predation for bright males are both well documented in numerous works (see Dill et al., 1999, and references therein).

Because fresh waters are optically turbid in comparison with pure sea waters, curves of photopic spectral sensitivity in freshwater fish are strongly displaced to the red part of the spectrum. For example, the maximum of spectral sensitivity in threespined stickleback, Gasterosteus aculeatus, is near 605 nm (Rowe et al., 2004). It means that for eyes of freshwater fish red and orange colors are brighter than all other equipower monochromatic colors, and this feature occurs in nuptial signaling coloration.

The nature allows males of freshwater fish to practice several strategies to find trade-offs between conspicuousness for sexual mates and crypticity for potential predators, including plasticity in nuptial color development (e.g., Endler, 1983; Candolin, 1998; Ruell et al., 2013). In this context, an ability to develop bright red and orange colors in the under less illuminated parts of the fish’s body, in conformity with the theory of color countershading in fresh waters, is the primary.

Indeed, red and orange colors occur in breeding males just in the under parts of their bodies such as breast, ventral part, belly and the lower fins. An important role of this elements in nuptial coloration of males is documented in guppy, Poecilia reticulata (Endler, 1983; Kodric-Brown, 1985), and other species of genus Poecilia, threespined stickleback, G. aculeatus (Rowe et al., 2004), European bitterling, Rhodeus sericeus (Candolin & Reynolds, 2001), and in other spesies of genus Rhodeus, as well as in males of other freshwater fish. In some cases red and orange colors occur in the upper most illuminated parts of the fish’s body, but patterns of this type will be considered separately.

According to Kodric-Brown (1998), breeding males with red fins occur in many families of North American freshwater fish, including minnows (Cyprinidae), suckers (Catostomidae), killifish (Fundulidae), sunfish (Centrarchidae), darters (Percidae) aa well as cichlids (Cichlidae).

Generally, bright red and orange colors are conspicuous at the shot distance for sexual mates, but are cryptic in the countershading complex at the longer (that is optically thick) distances for potential predators. According to Evans & Norris (1996), red pigmentation of the fish’s body cannot be assessed accurately under green light or hereof if viewed through the water column, as the natural green filter.

Vorobyev et al. (2001) demonstrate how fish can see other fish through the water column.

Basic References

Candolin U. 1998. Reproduction under predation risk and the trade-off between current and future reproduction in the threespine stickleback. Proceedings of the Royal Society, Biological Sciences 265, 1171-1175

Candolin U., Reynolds J.D. 2001. Sexual signaling in the European bitterling: females learn the truth by direct inspection of the resource. Behavioral Ecology 12, 407-411

Dill L.M., HedrickA.V., Fraser A. 1999. Male mating strategies under predation risk: do females call the shots? Behavioral Ecology 10, 452-461

Endler J.A. 1983. Natural and sexual selection on color patterns in poeciliid fishes. Environmental Biology of Fishes 9, 173-190

Evans M.R., Norris K. 1996. ... Read more »