Frequency and distribution patterns of Saprolegnia infection in wild and hatchery‐reared brown trout Salmo trutta L. and char Salvelinus alpinus (L.)

Abstract

. Fungal infection of sexually mature brown trout and char was associated with a particular type of Saprolegnia exhibiting a low degree of homothallic sexuality. Hatchery‐reared brown trout were more severely infected (in terms of the % area of the body covered with the fungus) than were wild fish. The fins of hatchery‐reared fish were particularly prone to Saprolegnia infection regardless of sex. In wild brown trout, a sexual difference in the pattern of infection was demonstrated. The flanks of the male fish appeared to be more prone to infection when compared with the female and there was a greater susceptibility of the caudal and ventral fin of the female when compared with the male. Evidence is presented which suggests that the incidence of infection in mature male salmonid fish prior to spawning is significantly greater than in the females. This difference may not be apparent in spent fish after spawning. These findings are discussed in relation to the background concentration of fungal spores in the water, the behavioural characteristics of spawning fish and differences in epidermal structure.

Season and physiological parameters modulate salmonid leucocyte androgen receptor affinity and abundance

“…This, along with the immunosuppressive action of endogenous cortisol (also high in spawning salmonids: Bry, 1985), might help explain why sexually mature trout experience increased susceptibility to disease (Richards & Pickering, 1978;Robertson, 1979;Pickering & Christie, 1980). An 18 h confinement stress also led to lower leucocyte androgen receptor a$nity.…”

“…Frequency of ectoparasitic infestation increases in sexually mature brown trout, Salmo trutta (Richards & Pickering, 1978;Pickering & Christie, 1980), and rainbow trout, Oncorhynchus mykiss (Robertson, 1979), and the bactericidal activity of rainbow trout serum decreases at the time of spawning, both at the natural spawning time and in photoperiod-shifted spawners (Iida et al, 1989). Immune dysfunction during the reproductive period has been linked to increased plasma levels of androgens (Cross & Willoughby, 1989;Saad et al, 1990;Slater & Schreck, 1993) and may be compounded by increased plasma levels of corticosteroids (Slater & Schreck, 1993).…”

Histological structure of the skin of Arctic charr, Salvelinus alpinus (L.) from Spitsbergen

“…Thus these body parts in females are the most exposed to mechanical injury. It seems logical that the female skin in these body regions in salmonids should be thicker and richer in mucous cells, since according to Richards and Pickering (1978), it also prevents infection with Saprolegnia fungus. In the examined males of S. alpinus the skin in all the studied body areas was thinner and contained clearly fewer mucous cells.…”

Effects of nitrate and the pathogenic water mold Saprolegnia on survival of amphibian larvae

“…Fishes and amphibians may also be infected by Saprolegnia via contact with infected soil (Kiesecker et al 2001b). Host species show strong interspecific variation in their susceptibility to infection (Richards & Pickering 1978, Wood & Willoughby 1986, Kiesecker & Blaustein 1995. Factors such as water temperature, pH, pollution, exposure to UV-B radiation, injury from biting, silt, and host behavior may modify the effects of Saprolegnia on its hosts (MacGregor 1921, Strijbosch 1979, Walls & Jaeger 1987, Banks & Beebee 1988, Carballo & Muñoz 1991, Bly et al 1993, Pickering 1994, Carballo et al 1995, Kiesecker & Blaustein 1995, Lefcort et al 1997.…”