Tom Schaffer
Ecology of Fishes 511
Wednesday
My two species are the Lake Sturgeon and the Barndoor Skate
Benson, A. and Sutton, T. 2005. Seasonal Movement Patterns and Habitat Preferences of
Age-0 Lake Sturgeon in the Lower Peshtigo River, Wisconsin. Transactions of the
American Fishes Society 134:1400-1409.
1. The habitat preferences of age-0 lake sturgeon in the Peshtigo River are based on
water velocity, temperature, and water depth.
2. Immature lake sturgeon move on a daily basis to parts of the Peshtigo River
where conditions are favorable, where water velocity was no greater than .6 m/s,
median water depth was between .56 and 1.3 m, and median temperature was
between 11.44°C and 25.3°C.
3. There was one figure in the paper, a map of the Peshtigo river, showing where the
data collection sites were. It was useful to be able to gain a perspective of the
data collection sites and their relationship to each other.
Hughes, T., Lowie, C., and Haynes, J. 2005. Age, Growth, Relative Abundance, and
Scuba Capture of a New or Recovering Spawning Population of Lake Sturgeon in the
Lower Niagara River, New York. North American Journal of Fisheries Management
25:1263-1272.
1. Over fishing by humans has caused a change in the Lake Sturgeon Population in
the Lower Niagara River, New York.
2. Human over fishing has caused this sharp decline in the Lake Sturgeon
population, as well as by pollution caused by humans, the author recommends,
that the Sturgeons here be classified as a recovering species, and that future
sampling be done up stream of power plants to get a better idea of sturgeon
population.
3. There were several figures in the paper, a map of the Lower Niagara River gave a
good idea of how pollution got into the river, and various graphs showed
graphically how the population of Sturgeons has significantly declined, with most
fish caught being under 10 years of age, with no individuals above the age of 23,
very significant for a fish that can live to be over 100 years old.
Casey, J. and Myers, R. 1998. Near Extinction of a Large, Widely Distributed Fish.
Science 281:690-691.
1. The populations of Barndoor Skates are being affected by commercial fishing and
competing teleosts.
2. Barndoor Skates are around 1 m in total width, and are being accidentally caught
by trawl nets with hole diameters of 7-14 cm. 45 years ago, off the coast of
Newfoundland, researchers recorded Barndoor skates in about 10% of their tows,
and none have been caught in the last 20 years. Also, Elasmobranchs have a
lower natural mortality than teleosts, and at low population levels, they cannot
respond to pressures as well as teleosts, therefore leading to extinction.
Tom Schaffer
Ecology of Fishes 511
Wednesday
3. There were two figures in the paper, a map of the fisheries, and a series of graphs
showing decline in biomass of Barndoor Skates over the last 40 years. Both gave
a good graphical representation of where the fisheries described in the paper were
located, and how significant the decrease in biomass of barndoor skates has been.
Northeast Fisheries Science Center. 2003. Essential Fish Habitat Source Document:
Barndoor Skate, Dipturus laevis Life History and Habitat Characteristics. NOAA
Technical Memorandum NMFS-NE-173.
1. Populations of Barndoor Skate require a specific habitat with temperature, bottom
depth, and salinity being the most important aspects.
2. Most barndoor skates were found to be living at a bottom depth between 71 m and
120 m with the highest concentration at 81-90 m, temperatures between 3°C and
8° and salinity between 32 ppt and 36 ppt. Salinity appears to be the most
constant predicting variable of likely habitat.
3. There were numerous maps showing the presence of barndoor skates at various
stages of development off of the coast of New England. These figures were
essential in visualizing how widespread these animals are. There were also
several bar graphs showing aboitic factors that influenced barndoor skate habitat,
which were useful for visualizing optimum factors that influenced the habitats of
the barndoor skate.