Reproduction and Spawning

 

Spawning Brook Trout

Brook trout spawn in the fall over areas of groundwater upwelling on the Nipigon River.

DaveSB

  Brook trout spawn in the fall over areas of groundwater upwelling on the Nipigon River. They require high quality cold water environments for survival and reproduction. Brook trout spawning areas in the Nipigon River have been impacted by the regulation of the river for power generation. Forgan Lake, created by the Pine Portage dam, flooded the best brook trout waters of the river, including Virgin Falls. Numerous other factors affect brook trout spawning include: competition for spawning beds by introduced Pacific Salmon; eggs that are highly susceptible to siltation; scouring from log drives; and the impacts of gravel extraction on areas of groundwater upwelling (Swainson 2001a).

    Roving angler surveys were conducted sporadically on the river between 1987 and 1994 and volunteer angler diary programs have been in place since 1988. Brook trout fishing quality has varied from one fish per 20 hours of fishing in 1987 to one fish per 7-8 hours in 1994 and has stayed at this average ever since. Tagging and tracking studies have also provided information about brook trout movements and migration patterns. Some brook trout have been caught and released as many as three times in the same location. Brook trout tagged in the Lower River have been recovered as far away as Rossport and in the Gravel River area. In 1989 and 1990, brook trout in Jessie Lake and the lower Nipigon River were implanted with radio and sonic transmitters and tracked to locate their spawning beds. Field studies from 1988 to 1990 demonstrated that fluctuating water levels, caused by hydroelectric dam operations, exposed up to 90% (21 of 23) of the identified brook trout redds in the Nipigon River causing desiccation and freezing during the spawning and incubation period.

    In response to public demand to save the Nipigon brook trout, as part of the Nipigon District Fisheries Management Plan 1989- 2000, a detailed restoration plan was developed and implemented in 1989. Flow tests were conducted to determine minimum requirements to allow spawning and to protect brook trout redds during the incubation period. Spawning habitat was created by constructing two artificial upwelling areas by piping and dispersing groundwater up through gravel in the Nipigon River. In addition, a large area (1000 m2) and several small (1.5 m2) areas where groundwater discharged through unsuitable substrate were improved by replacing or covering the native bottom material with suitable gravel materials. To provide additional spawning and nursery habitat, a small groundwater fed tributary was reshaped and resurfaced with gravel substrate. Nursery habitat was also enhanced in a nearby, small groundwater fed tributary by excavating a 31 m2 pool. To provide access for spawning fish and to avoid stranding during rapid drawdown events caused by hydro-electric dam operations, the littoral zone was recontoured near a natural spawning area and near the habitat enhancement projects.

Since the establishment of the flow agreement a maximum of 20% of the identified brook trout redds have been exposed to desiccation and freezing. Through a public consultation process directed by the Remedial Action Plan for the Nipigon Bay, the 1990 interim flow agreement was expanded in 1994 to a Watershed Management Plan for the Nipigon River and Lake Nipigon and from this a Nipigon River Operating Plan was developed in 1999. The plan gives first priority to protecting brook trout habitat while considering the needs of other stakeholders.

Reproduction

The life cycle of the Brook Trout (example only)

lifecycle

During the summer months adult Brook Trout are usually found in larger streams and lakes. In late summer and early fall as the length of the day begins to shorten the Brook Trout begin to migrate out of the lakes and up the larger streams into the smaller headwater steams. Here they seek out a spawning location in gravel beds in streams with cold, well-oxygenated water. Brook Trout seem to seek out areas where upwelling springs occur. The streams are usually fairly shallow, but not so shallow that the bed will be damaged by ice during the winter. Some Brook Trout may remain in lakes and spawn in gravel beds over upwelling springs. Females are capable of detecting upwelling springs or other gravel areas with ground-water flow and often deposit their eggs in these habitats.

Spawning usually begins in October and continues into the fall.  In spawning the female Brook Trout prepares a depression in the gravel of a stream using her tail fin.   This depression is called the redd. Hovering over the redd the female releases 15-60 pea sized eggs into the redd. As the eggs settle into the redd the male, who hovers nearby, releases a cloud of sperm, or milt, and the eggs are fertilized.  Individual males may display some territoriality with aggression increasing when joined by a female. The female then uses her tail fin to sweep the gravel back over the eggs and then moves on to construct another redd. The total number of eggs a female lays depends on her size, larger females laying more eggs.  The number of eggs produced by a female varies with her size.  A 4-inch fish produces less than 100 eggs; a 14 or 15-inch fish produces over 2,000 eggs, while a 22-inch fish will produce over 5,000 eggs.  One male and female perform actual spawning; however, each may spawn with different mates during the reproductive period. 

Several different accounts of the spawning act have been recorded for brook trout.  One account stated that the female turned on its side, flipped its tail several times and the eggs shot out.  Another reported that the female took a position on the bottom of the nest, with pectoral and pelvic fins spread against the stones, and at her side the male arched his body to hold the female against the bottom and both vibrating intensely as eggs and milt were discharged.  There are several extrusions followed by a resting period.  The eggs are adhesive for a short period after extrusion which allows those not lodged in gravel from being washed away.   After spawning is completed the female covers the eggs with gravel in a similar manner as when she constructed the redd. 

The length of the incubation period varies according to the temperature - at lower temperatures the incubation period is longer. For example, in 35 Fº water, the incubation period is about 144 days; in 50 Fº water, the incubation is only 44 days. The effect of temperature on the length of the incubation period is adaptive. No matter when during the fall/winter the eggs are laid, it allows the eggs to hatch in March and April when food for the larvae becomes abundant.

Newly hatched trout are referred to as alevin. They somewhat resemble tadpoles because of the pendulous yolk sacs protruding from their undersides. Alevin remain in the protective gravel of the redd as they use up the stored nutrients in the yolk sac.

When the nutrients are gone the young salmon emerge ("swim-up") from the gravel. At this stage they are referred to as fry. The fry leave the redd area and move to shallow water where they can find some protection from predators. After several weeks a series of dark vertical bands called parr marks appear along the sides of the young trout and they are now referred to as parr. The Brook Trout lose these marks as they grow, eventually becoming juveniles, then adults.

 

 

A male brook trout in full spawning colours

I took John out for his first trip to Brook Trout Heaven and on his first cast, this is what he caught. Beginners luck!!!

 

Kuzikfallmale