Updates: 2005

Belle Isle Spawning: May 16 - 18, 2005

Monday, May 16th, 2005
Three GLSC divers (Marc Blouin, Jeff Allen, and Greg Kennedy) conducted a general video survey of the substrate that make up the sturgeon spawning control site, and video documented the 12 egg mats (3 gangs) that occupy the site. Egg mat gangs at this site run parallel along a gently sloping ridge, where the shore-ward gang (designated 'Z-A') is the shallowest (19-21'), the middle gang (Z-B) is in 22 - 23', and the channel side gang (Z-C) is the deepest at 25-27'. In addition, the dive team evaluated the base substrate that comprised the area, and concluded that the majority of the substrate in this area (control site) consists primarily of zebra mussels on a bed of hard pan clay and silt. We also collected a small sample of sediment that appeared to in-fill behind the egg mats and small embedded rocks.

The dive team then moved shore-ward, up to the top of the ridge that runs adjacent to the egg mat gangs, and is suspected to be a natural walleye spawning site. The dive team observed several small (roughly 3' x 4') patches of piled and embedded rocks that make up most of the top of the ridge, in 15' of water. No evidence of any egg deposition was observed during our dive, however. The final objective was to collect 1/4 m quadrat suction samples in the vicinity of the egg mats in an attempt to compare egg density to that observed on the egg mats. Unfortunately, we brought the suction pump down with us, but forgot to bring the 1/4 m quadrat (perils of first-time sampling), so we compromised by conducting a qualitative suction sample in the immediate vicinity (no measured area) of the dive line anchor. We concluded that the water temperature was still too cold to look for sturgeon eggs, so we decided to post-pone suction sampling until the river achieves at least 13°C. Water temperature on the bottom was abut 48°f (8.9°C?), and visibility was about 1 - 1.5 m.

Tuesday, May 17th, 2005
The GLSC dive team continued the video survey at the Limestone reef. Water temperature and visibility were about the same as on Monday (48° and 1+ m). Some minor adjustment was made to the "A" and "B" gang anchors, otherwise all egg mats were found to be on the reef and in fishing condition. Video documentation was made of all 12 egg mats. Video documentation was also made showing the in-filling of sediment within the rock piles that make up this reef.

Sediment does appear to be accumulating (at least to a small degree) within the rock interstices, and also along the back end of the reef. Two samples were collected on the reef for analysis as well - one along the shore-side of the reef edge, and one roughly in the middle of the reef. No large fish were observed on the reef, or in the immediate area, and no evidence of egg deposition was observed either. A few Goby were observed swimming through the rock interstices and along the back end of the reef.

Wednesday, May 18th, 2005
The GLSC dive team continued the video survey at the last two reefs - the cinder and fieldstone (cobble) reefs. Water temperature and visibility at these two reefs were slightly warmer than the previous two days (51°f and 1.5 - 2 m).
Cinder Reef: Initial observations of the cinder reef indicated that extensive "cleaning" had taken place on the rock material since the last time we had observed this reef. Our last dive indicated extensive algal growth and sedimentation, but this dive showed a majority of the reef free of the "crud". In addition, as we worked our hands through the cinder material, we observed what appeared to be many sucker eggs (and small numbers of walleye (?) eggs) drifting free.

We attempted to video document both the clean versus clogged portions of the reef, and the evidence of eggs drifting loose when we disturbed the material. We also video documented all 12 egg mats - all mats were found on the reef and in fishing condition. We did not try to observe any eggs on the mats, as they were just sampled on the previous day. However, there was at least one instance where an egg was visible on the mat. Digging into the reef material indicated that the cleaning only went abut 1/2 -1" deep. As we dug into the reef material, we observed that the underlying portions of the reef were completely in-filled with sediment. We tried to collect 2 samples of the sediment, but this proved difficult due to the mixed nature of the sediment with the small cinders. We will try to take a core of the material - reef and all - the next time we dive the reef, in an attempt to better examine the sediment in-filling.

Fieldstone (cobble) reef
Dive operations concluded at the fieldstone reef. Conditions at the fieldstone reefs closely resemble those of the limestone reef. Video documentation of all 12 egg mats were conducted, as well as the general condition of the reef. Gang "C" - the gang closest to the river channel, was strung right along the outer edge, so we repositioned it in to the reef about 6 - 10' , otherwise all egg mats were found on the reef and in fishing condition. Two sediment samples were collected; one along Gang "B" and the other along Gang "B". No evidence of egg deposition was observed.

Content Credit: Bruce Manny, science lead

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