Characteristics of the Gaspereau River

Alewife Stock and Fishery - 1998.

The Gaspereau River - Black River watershed, which was extensively modified for hydro-electric generation between 1910 and 1950, supports a stock of anadromous alewives (Alosa pseudoharengus) that is fished both commercially and recreationally as it ascends the river to spawn. Since 1964, the annual spawning run in this river has averaged about 1.1 million fish. The 1998 run consisted of about 550,000 fish, known to be the smallest run since 1992. The catch in 1998 (2,800 pails) was smaller than 80% of the catches since 1964. Reduced abundance of age 4 alewives accounted for 75% of the reduction in stock size since 1997.

A total count of alewives ascending the fish ladder at White Rock in 1998 (upstream of most fishing activities) indicated that over 171,000 alewives ascended the ladder, the highest escapement from the fishery of the 7 years for which counts are available. A partial count of alewives ascending the ladder at Lanes Mill was used to estimate that just under 97,000 alewives entered Gaspereau Lake to spawn this year. Estimates of transit time from the White Rock ladder to Gaspereau Lake ranged between 2 and 7 days.

Alewives sampled during 1998 were the smallest on average compared to those from 5 previous assessments. Based on back-calculated length-at-age, this reduction in size apparently occurred as a result of poor growth at sea during 1997.

The ecology of young-of-the-year (YOY) alewives in Gaspereau Lake was studied during the summer and fall of 1998 in order to collect data useful for the development of management strategies for these fish in this watershed. Larval abundance was higher in 1998 than in 1997, an observation consistent with the increased spawner abundance. Zooplankton abundance was also higher in 1998, suggesting an adequate supply of food.

YOY out-migration was monitored at the outlet to the Gaspereau River between early July and mid-November. Out-migration rates were highest during the third week of September. Just under 0.5 million YOY were estimated to have exited the lake via this outlet during the study period. Alewives were still present in the lake in late September, and an estimated 1.1 million moved downstream when the control gate at Forest Home was opened during the third week of this month. YOY out-migrants were large enough for the Trout River Pond fish diversion screen to be effective by mid-August.

River flow in the old Gaspereau River (10 c.f.s.) was about 1/3 that of 1997. Adult alewives did not appear willing to move downstream at the reduced flow, and many remained in the system until the gate at Forest Home was opened in late September. Adults were not observed taking this route in 1997.

Age 1+ alewives were observed leaving Gaspereau Lake in the fall, suggesting that not all alewives will emigrate if the Forest Home control gate is kept closed into the fall as was the case in 1997.