3rd Bay of Fundy Science Workshop
Understanding Change in the Bay of Fundy Ecosystem
From Invertebrates to Fish
Horse Mussel Reef Project in the Inner Bay of Fundy
Habitat Requirements of Striped Bass (Morone saxatilis) in Eastern
Canada With an Emphasis on the Shubenacadie-Stewiacke Rivers in the Inner Bay of Fundy,
Nova Scotia
Reproductive Cycling in Mummichogs (Fundulus heteroclitus) in
Bay of Fundy Estuaries Close to Saint John, NB
Horse Mussel Reef
Project in the Inner Bay of Fundy David J. Wildish¹, Hugh M.
Akagi¹ and Gordon B.J. Fader²,
¹Fisheries and Oceans Canada, Biological Station, St. Andrews NB
E0G 2X0
²Natural Resources Canada, Geological Survey of Canada (Atlantic),
Bedford Institute of Oceanography, Dartmouth NS B2Y 4A2
Abstract
The purpose of the work begun in 1996 was to demonstrate the capability of acoustic methods, such as side-scan sonar, high resolution seismic reflecting systems and multibeam swath bathymetry, to spatially delimit the subtidal reefs of keystone horse mussels, Modiolus modiolus. We believe that the capability of acoustic methods to delimit the spatial limits of benthos and monitor temporal changes is worth investigating in much greater detail than has been done so far.
To date, we have shown that features identified by side-scan sonar and seismic reflectors are M. modiolus reefs by identifying them by colour video camera mounted on an ROV (Wildish et al. 1998a). Preliminary analysis of the side-scan sonar data obtained in 1997 suggests that there are 14 geological provinces (Wildish and Fader 1998; Wildish et al. 1998b). Of the provinces, only five commonly contain horse mussels: sand with bioherms, gravel/cobble, gravel/scallop bed, mottled gravel and glacio-marine mud. Horse mussel reefs can only be spatially determined from the first of these provinces, as all others have acoustic scattering due to other features, e.g. boulders that mask the mussel distribution. In all, 673 horse mussels were sampled from the five geological provinces and subjected to population and growth analyses (Wildish et al. 1998b). Results show that three population groups were present, each linked to particular geological provinces:
Group 1 - sand with bioherms -fast growth
Group 2 - gravel/scallop bed -intermediate growth
Group 3 - gravel/cobble, mottled gravel -slow growth
Work still to be completed includes:
• multi-beam swath bathymetry survey of the inner Bay, scheduled for June 15-24,
1999
• digitization and work-up of side-scan data for 1997, inclusive of mapping the
results
• experimental work to determine the mechanism of the horse mussel growth rate
differences, particularly testing hypotheses that (a) fast flows inhibit growth, and (b)
gravel/cobble substrates cause "skimming flows" which inhibits seston mixing
within the benthic boundary layer.
References
Wildish, D.J., G.B.J. Fader, P. Lawton, and R.J. MacDonald. 1998a. "The Acoustic Detection and Characteristics of Sublittoral Bivalve Reefs in the Bay of Fundy" In Con. Shelf Res. 18:105-113.
Wildish, D.J. and G.B.J. Fader. 1998. "Pelagic-benthic Coupling in the Bay of Fundy" In Hydrobiologia 375/376:369-380.
Wildish, D.J., et al. (+ 22 other authors). 1998b. "Population Analyses of Horse Mussels of the Inner Bay of Fundy Based on Estimated Age, Valve Allometry and Biomass" In Can. Tech. Rep. Fish. Aquat. Sci. 2257: 43p.
Habitat
Requirements of Striped Bass (Morone saxatilis) in Eastern Canada With an Emphasis on the
Shubenacadie-Stewiacke Rivers in the Inner Bay of Fundy, Nova Scotia Rodney
G. Bradford,
Diadromous Fish Division, Department of Fisheries and Oceans,
Halifax NS B3J 2S7
Abstract
At least five spawning populations of striped bass once existed within eastern Canada: the St. Lawrence River, Quebec, the Miramichi and Saint John rivers in New Brunswick, and the Shubenacadie-Stewiacke and Annapolis rivers in Nova Scotia. The Miramichi and Shubenacadie-Stewiacke rivers are the only confirmed sites where striped bass now reproduce annually. These populations are genetically discrete and both differ from striped bass of American origin. Habitat loss is believed to have been the greatest contributing factor to past extirpations of striped bass from Canadian rivers and estuaries. The remaining populations are susceptible to alterations to essential spawning, rearing and wintering habitat through continuing human land-and sea-use practices. Within the Shubenacadie-Stewiacke system, alterations to essential habitat may have occurred as a consequence of the construction of an extensive networks of dykes and the wide-spread utilization of culverts, aboiteaus and causeways on tidal waterways. The consequences in terms of permanent losses of fish production and to population viability are largely unknown but are presently under investigation.
Reproductive
Cycling in Mummichogs (Fundulus heteroclitus) in Bay of Fundy Estuaries Close to Saint
John, NB D.L. MacLatchy, B. Kerin and F. Leusch,
Department of Biology and Centre for Coastal Studies and
Aquaculture,
University of New Brunswick, Saint John NB E2L 4L5
Abstract
There is increasing evidence that environmental contaminants and pharmaceutical agents have sub-lethal toxic effects on the reproductive endocrine systems of fish. Previous work in our lab utilized caged mummichogs (Fundulus heteroclitus) throughout the Saint John Harbour (SJH). The SJH receives effluents from a number of major industries in addition to treated and untreated sewage. Our studies indicated that there are site-to-site differences in reproductive endocrine status that can be correlated to caging within particular waste water microenvironments. Hampering our interpretations of that work is our lack of information about the endogenous rhythms of the reproductive endocrine system of wild mummichogs living near SJH. During the summer of 1998, mummichogs were collected from four sites in the Bay of Fundy near the SJH. At each site, mummichogs were captured by dog food-baited minnow traps at approximately two-week intervals. Adult fish were weighed, measured, bled and the gonads removed and weighed. Plasma levels of the reproductive steroids [testosterone (T) and 11-ketotestosterone (11-KT) in males and T and 17 -estradiol (E2) in females] were measured by radioimmunoassay. At all sites, 11-KT in males was high in May and decreased throughout the summer. Hormone and gonadal development patterns differed amongst the sites; T levels, however, always peaked prior to or during gonadal peaks. Males and females within each site showed similar patterns. The two sites furthest from the SJH were the most similar. However, it is too early to tell if site differences can be linked in any way to SJH pollution, natural variations amongst the populations, or differing habitats.
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