Jm. Casselman, SURVIVAL AND DEVELOPMENT OF LAKE TROUT EGGS AND FRY IN EASTERN LAKE-ONTARIO - IN-SITU INCUBATION, YORKSHIRE BAR, 1989-1993, Journal of Great Lakes research, 21, 1995, pp. 384-399
Restricted production of lake trout fry in eastern Lake Ontario limits
recruitment and the establishment of a self-sustaining population. To
examine the survival and development of eggs and fry, incubation stud
ies were conducted from 1989 to 1993 in situ on Yorkshire Bar and in t
he laboratory with untreated surface water from Lake on the Mountain.
Eggs were collected at spawning time (16 October-9 November, median 24
October) from Lakes Ontario and Manitou, fertilized, and held individ
ually for an average of 162 days in 290 50-cell Plexiglas incubation c
hambers. On Yorkshire Bar, significantly more eggs died (P < 0.001, 1.
65x mean absolute difference (<Delta(x)over bar>) = 14%), and regardle
ss of egg source, there were fewer hatched fry than in the laboratory
(P < 0.001, 0.63x, <Delta(x)over bar> = 29%); 75% of the fry that hatc
hed died early in the incubation period, and 42% of these completely d
ecomposed and disappeared by the end of the incubation period, leaving
empty incubation cells. Significantly fewer live fry were produced on
Yorkshire Bar than in the laboratory (11.2% versus 69.2%, <Delta(x)ov
er bar> = 58%). Abundance of live fry was inversely related to cumulat
ive thermal units (CTU). Increased exposure on the bar from 370 to 690
CTU decreased survival from 25% to 0. In eastern Lake Ontario, spawni
ng has been observed at a mean water temperature of 11.5 degrees C (29
October) but ranged between 12.7 degrees C (19 October) and 8.8 degre
es C (14 November); fry survival on 1 May from these dates and tempera
tures would be 10%, 0%, and 21%, respectively. If the mean temperature
at spawning were 2 degrees C lower (9.5 degrees C, 9 days later), pro
duction of fry on 1 May would be almost double (19% vs. 10%). Spawning
at lower temperatures would increase fry production on shoals like Yo
rkshire Bar. Temperature inversely affects fry survival, especially if
the spawning substrate is degraded by organic sedimentation, which ca
uses increased biological oxygen demand and reduces oxygen concentrati
ons.