Wednesday, March 30, 2011

Surveying for Oregon Spotted Frogs in Western Washington

Love is in the air this time of year for many species of frogs around western Washington. With cool spring rain, male frogs find suitable areas for attracting a female mate, then use a unique call to attract females to the area. Many species of frogs will return to the water body where they were born to find a suitable mate.

Here in western Washington, several different kinds of frogs are found, including Pacific tree frogs and red-legged frogs. One species of special concern to U.S. Fish and Wildlife Service (USFWS) biologists is the Oregon spotted frog. Once widespread, this frog species may have been lost from at least 90 percent of its former range. Causes for the decline in frog populations include loss of habitat, non-native plant invasions, and the introduction of exotic predators such as bullfrogs.

Oregon spotted frog eggs
Around this time each year, USFWS biologists travel to the three areas in western Washington where Oregon spotted frogs are still known to persist. A survey of the area is performed to count the number of frog egg masses. When an egg mass is found, it is marked and monitored as it develops. Eggs typically hatch in 3 weeks and, once hatched, the young tadpoles graze on bacteria, algae, and plant tissue in the water.  By monitoring the egg masses, biologists can keep a close eye on the status of these populations.

Females deposit egg masses in shallow, often temporary, pools no more than 6 inches deep. Sometimes, though, the frogs choose areas where the water level drops, leaving the eggs high and dry. As you can see from the picture below, several Oregon spotted frog pairs chose the same area to lay their eggs. This large mass, which contained 16 individual egg masses, was found in an area where the water level had dropped. With careful and gentle hands, the eggs were moved by one of our biologists into an area that contained a bit more water. There the eggs will be able to develop and, in a couple of weeks, little tadpoles will hatch out and begin to feed.

Large egg mass before move to wetter habitat

Biologist's coat being used to move egg masses

Gently placing frog eggs in new home
With some habitat protection, population monitoring, and a little assistance from their two-footed friends, these Oregon spotted frogs will hopefully continue this cycle for many years to come in western Washington.

Friday, March 18, 2011

Hoh River Project - Field Work 3

Seining in the Hoh River
 We continued field work for the Hoh River Engineered Logjam (ELJ) study in March 2011. Fish abundance, density, and diversity were assessed using seining and mark-recapture methods.  
At each of the two sites, we captured and marked fish with Bismarck Brown on one night, then recaptured fish the following night. We caught a total of 419 fish during the surveys. Recapture rates for coho and Chinook salmon at Hoh I and Hoh II sites were 11% and 13%, respectively. From these numbers, we will be able to make rough population estimates. Additionally, we recaptured 1 fish that we had PIT-tagged at the Hoh I (ELJ) site last year.
It was a fun-filled but hectic couple of days as we scrambled to get everything done before forecasted rain increased river discharge to a point where we couldn’t work, which would have washed away all of our sampling efforts. We compressed all of our work into two nights; one night for marking at both sites and one night for recapture at both sites. The work was completed just in time, with river discharge increasing to 5,000 cfs the day after we finished.
Data entry, checking, and analysis will be completed from April through May.  A final report will be completed by June 30, 2011. 

Thursday, March 10, 2011

How Many Salmon Live in a River?

Screw trap in the Big Quilcene River
It’s that time of year again when young Big Quilcene River coho salmon (smolts) begin to outgrow the home they have lived in for the past year. Soon they will begin to make their way downstream and into Hood Canal where they will find habitat that will allow them to continue to grow. The fish will spend up to 2 years there, out of the fresh water of the Big Quilcene River, eating and growing to adult size.  Some of these fish will return to the river after only 1 year; these fish are called jacks. The majority, though, will return after spending 2 full years in the ocean.
Staff preparing to install trap
To monitor the number of juvenile smolts leaving the river and going out to the salt water, we installed a trap that gently collects fish as they swim downstream. The trap we installed is a screw trap; it is made of a metal cone in the shape of a funnel that spins in the water. This type of trap allows fish to be funneled through the trap into a live box where they are held. The cone and live box are suspended on the water by two pontoons. An employee from our office will check the trap daily and take data on any fish caught in it. Any coho smolts caught in the trap are tagged and then released to complete their journey to the ocean. This tag will allow us to identify these fish when they return as adults. 

The trap will remain in the Big Quilcene River for the next couple of months, the entire time period when fish are headed out of the river to the ocean.  From the data collected during this time, we will be able to determine how many coho salmon left the Big Quilcene River for the ocean and how many fish call the Big Quilcene River home.

Looking upstream at the screw trap