Smolt Monitoring in Marin CountyApril 8 2017
My name is Neely and I am a field scientist in training. Here I will document a fisheries field study and hopefully inspire some ocean stewards along the way.
About 1 in 5 of the homeric-journeying central coast California salmonids are born and die in the Lagunitas Creek Watershed in Marin County. Unfortunately this fish population is estimated to be down to about 8% of it's historic size. Salmon Protection and Watershed Network (SPAWN) works with county and state agencies to count, monitor and evaluate the state of the population and best practices to save our fishy friends (aka keystone species).Read background
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2017 weekly smolt counts are congruent with historical data that shows the largest push of out-migrating smolts is the last week of April.
Pictured is about what 2017 final tallies will look like. Year to year comparisons to follow-up in the wrap-up.
09:30: *PVC Pipe found disconnected from live trap this morning. *
Couple handfuls of debris and a couple of parr were present in trap.
* Potential causes: *
- George, the resident deer, being clumsy as he crosses the creek.
- PVC joint had been sitting loose and large clump of debris may have jostled it free.
- The downstream landowner (he's a grumpy, anti-science individual) was being vindictive -- although this is highly unlikely.
Oh well! On the upside--it's the end of the season and there would not have been many smolts to count. On the downside, there is no down side. When we start getting one or less smolts a day for three days in a row, it's time to close the season.
They grow up so fast!
Q: Why are the freshwater fish less elusive?
A: I haven't been able to find a specific answer for why the freshwater natives are easier to catch. It seems that sometimes we catch the salmon fry by luck in the hand net and scoop out the California roaches with more ease.
Is this because of the species different life strategies? Or Intelligence? Or Fitness of the lineage?
My first thought was prey selection-which is well-established influence of selection. But the California roaches and salmonids look almost identical from the top and occupy the same freshwater habitat. So that might not be a solid answer.
I'm not well-versed on fish intelligence. Almost all fish are visual predators so it's hard to say for sure that salmon can see a net better than a native freshwater fish in the same water.
The final idea-- Almost 90% of all salmonid fry (everywhere) are going to either get eaten or die from disease or starve. The lineage of fish in this watershed have most recently survived ten years of drought and two El Nino events. So I would guess the stakes haven't been as high for the native freshwater fish (again, I don't have scientific studies backing up this idea) so they haven't evolved to be as fast or nimble.
It's an interesting question!
Salmonid Fry Growth
It used to take a good hour to chase down all the zippy little fry in our live trap box. They were about an inch long in mid-April.
A month later, it still takes a good hour to chase down all the zippy little fry in our live trap box because they are twice as large! No, it's not the exact same fish we're catching, but it is the same age group. I started taking extra notes to document fry growth because I felt like each week they went up a size class (You can check out what actually happened on the graph).
Salmonids come out of their nests in early Spring and will feast on whatever they can catch and fits in their mouth. In the beginning stages of life, this range is limited to small zooplankton. Eventually, they are fast enough to fit large zooplankton and will continue to eat their way up the freshwater food chain until their smolts.
The Steelhead young of the year we're seeing have graduated to eating bugs right when the first Spring insects are coming out in mass. The effect of added protein in a fry diet is reflective of adult salmonids gaining access to ocean nutrients and gaining anywhere from ten to thirty pounds in a year. Pretty amazing!
- Pictured is a 30-35mm California roach (I didn't have a small Steelhead to compare that day) next to 55-60mm Steelhead fry. *
Field Journal Musings:
[ ] Does today's colder water actually make the fish more active? Like are they really breathing more oxygenated water or are my hands numb so they seem more wiggly?
[ ] Do they fish notice the color morphs on each other? Note to self: look up past research on smolt color variations
[ ] Research has come out confirming fish talk to one another...do the recaptures tell the others about the net downstream? Can they hear each other screaming as I process them?
[ ] Coho parr are definitely smarter than the fresh water fish. It's easy to catch a California Roach. Coho literally dodge and weave the net.
Pictured is my co-worker Elizabeth, contemplating fish.
Today we counted 17 Coho smolts en route to Tomales Bay.
When I explain the life of a coho salmon to visitors at our trap, I liken the Coho's time in Lagunitas Watershed to years a kid spends in school. San Geronimo Creek is like elementary and middle school to Coho. The fish are slowly gaining a more adventurous diet (moving from tiny zooplankton to small insects) and they are growing very quickly. Lagunitas Creek is where a Coho spends it high school years in faster currents eating a full bug (protein!) diet. Finally, the time spend in the estuary, Tomales Bay, is like college. Coho undergo physiological changes from fresh to saltwater fish. At the end, it's like graduating from the eccentric but consistent college cafeteria into adult land--the Ocean!
Fish Eye View:
Awkward video of some steelhead fry in a jar. I lowered the camera into the jar to see if the view would be any more interesting (nope).
I want to talk about the bubbler that makes a brief cameo at the end.
Bubblers= aerators. They add oxygen to an aquatic environment.
What happens when a fish is in a small, enclosed environment, like a bucket, is they run out of oxygen.
Basic understanding of how fish breathe: Oxygen dissolved in water goes into a fish and out comes carbon dioxide. The CO2 is absorbs into the surrounding water and eventually dissipates into the atmosphere through aeration (bubbles!) An air bubble rising through water is simultaneously dissolving oxygen into the water and absorbing CO2 as it reaches the surface. A bubble popping at the surface is releasing CO2 into the atmosphere.
When aerators are on, they will try to keep oxygen levels at normal conditions.In a stream or creek, a lot more processes are at work incorporating dissolved oxygen into the ecosystem. In our case, leaving a ton of fish in a bucket of still water is risky! Adding a bubbler allows fish to breath normally while they are processed for the study.
In summary, an aerator is to a fish what a snorkel is to humans: a consist supply of breathable oxygen.
The many color morphs of California Coho Smolts!
Is it ...Diet? Genetics? The color of the bucket?
Blackish (actually that dark, not just the shadow!)
Silvery (A fully smolted Coho with no parr marks left. I like to think of these guys as the fish who have stopped eating and are dead set on swimming towards salt water).
Averages for the month:
Stream temperature: 12 C
Air Temperature: 22 C
Max stream flow: 1,032 cfs
Min stream flow: 8.67 cfs
Average coho weight: 105.4 g
Average coho length: 114.5 mm
* Total Salmonid takes: 397 *
- --Coho: 252
- --Steelhead: 10
"Take" defined by the Endangered Species Act means to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct. 397 times a fish was captured in our net in April, although only 262 new salmonids were counted. The other 145 account for recapture counts.
At this time last year, 334 coho smolts had been counted swimming to sea. This year we have only counted 252 coho smolts. We suspect that the 5 inches of rain early in the month kept us out of the creek and helped a lot of fish make a break for it.
When taking measurements, I call out the data to my volunteer scribe.
Fish we have never caught before are recorded as "New (N)" and I give them a fin clip. These fish go in the upstream bucket to mix with the greater out-migrating population of smolts. Pictured is a coho in a tray of water where it has just been measured and given an upper caudal clip.
My volunteers and coworkers kindly tolerate me talking to the fish. I imagine it's like going to the doctor as a kid and you make it through getting weighed and prodded, and then the doctor announces you're getting a shot...just a really rude surprise. So I know the words are meaningless but I try to gently talk the fish through the clip anyway.
Fish we re-capture, as marked by a fin clip, are recorded as "R" and moved to the downstream bucket. These fish will continue on their way to sea, down stream of the trap.
For each fish, the whole measuring process takes about 30 seconds.
In the second picture, I have walked a recently marked bucket of new salmonids up the creek. Instead of pouring the fish out, I gently tilt the bucket sideways so they can swim out. And I always say, "Good luck!"
Fish are not all a fyke net catches!
In the live trap this past week, researchers have found:
- blue gill
- golden roach
- three spine stickleback
- bull frog
- giant pacific newt
For personal interest in understanding the Lagunitas Watershed, SPAWN measures, weighs and photographs all species in case the data is useful for another project.
Preston up to bat processing fish. Biologists rotate every 10 fish for accuracy and cold fingers.
Preston will call out: species, fork length (mm), weight (g), fish condition, if a PIT tag is present, what the mark ID is/if present, and whether it's a new or recapture and the corresponding photo number. I record this info when I'm not puttering around on OpenExplorer. Woo!
Mark Recapture Method
Fun Fact: The first recorded mark recapture study was conducted on the population of London in 1629. If anyone knows how this guy was marking people...please let me know.
There are * 4 Assumptions * this method operates under:
- The population is closed. During the study, there are no deaths, births, immigration or emigration within the population in question. In order to ensure accuracy, it is assumed that during the study nothing is happening to disrupt the proportion of marked to unmarked fish.
- There is constant, equal chance for all individuals, marked or unmarked, to be caught during the study.
- There is time for marked individuals to randomly re-disperse into the greater population following each capture.
- Animals do not lose their marks.
The Mark Recapture Method answers a simple question: how many fish are in this population?
The principle: If a proportion of the population is marked, returns to the original population and then, after complete mixing, a second sample is taken, the proportion of marked individuals in the second sample will be the same as was marked initially in the total population.
R (marked recaptures) / T (total in second sample) = M (marked initially) / N (total population size)
N = (M *T ) / R
In these mark recapture studies, salmonids are marked with fin clips. A clip means a few fin rays are distinctively snipped. Salmonids normally accrue rips and tears on their fins so often fin clip schedules will include a small clip from two different fins. Markings are predetermined to correspond to calendar weeks. All participating agencies on the Lagunitas Watershed follow a coordinated fin clip schedule.
At the end of the smolt monitoring season, counts on how many fish were marked initially are compared to the total number of marked fish that were recaptured using R.
Past studies conducted by SPAWN and the Marin Municipal Watershed District (MMWD) have shown that the San Geronimo Creek Watershed, within the greater Lagunitas Watershed, contributes up to 50% of smolt production even though it accounts for only 10% of the watershed size.
Updates to follow on how counts are going and answers to follow on the ubiquitous "So, how are the salmon doing?"
The Big Red Cooler
Every morning this Spring there is a chance to catch smolts out migrating to the estuary. There is also a chance to catch a couple of wader-clad, caffeinated fish nerds hauling their red cooler of gear down to the creek.
This big red cooler holds all our precious fish monitoring equipment.
- Biomark reader
- Clipboard + data sheets + pencils
- Measuring tray
- A scale that trial and error taught us to keep in a gallon bag. (Is anything electronic truly waterproof?)
- Alka-seltzer tablets
- Scissors + small bottle of alcohol to disinfect scissors between each use
- Waterproof camera
Every smolt gets measured, weighed, fin-clipped, photographed and checked for a pit tag.
Saturday April 15th SPAWN Biologists trained some fishy citizen scientists!
Pictured is the day to day set-up including the fancy bucket a biologist sits on while we take smolt measurements.
Due to the ESA (Endangered Species Act), only those listed on federal research permits are allowed to actually handle the fish. SPAWN volunteers are crucial in efficient collection of data! Shown below is Preston demonstrating to a group how to tare the scale, and measure a fish.
My favorite picture of the day was Ken smiling as he held a jar we put a coho and steelhead fry in for quick comparison of characteristics. Ken normally works as a lab version of a researcher and is giving a day a week to work as a field researcher with us. You rock dude!
SPAWN's fyke trap consists of:
- a 9 x 4 ft bag net
- two wing walls (wooden frames covered with hardware cloth)
- three ropes
- three PVC pipes
- six t-posts
- a live trap (pvc box covered in mesh).
It takes about five hours to set up!
Picture below are the before and after photos of 2017 Fyke Trap: Round 2.
Adding to the random field biologist skill-set: sewing!
12:00 * Getting ready to set our trusty, weather-beaten fyke trap back up this afternoon.*
Never thought I'd be spending afternoons sitting in a redwood grove with a one inch needle and reel of fishing line mending a net.
SPAWN is stoked to train our Citizen Scientists tomorrow morning on salmonid ID and monitoring protocol. We're a ambitious non-profit, but SPAWN is small. And we couldn't efficiently collect the quality and amount of data we get every year without the help of our dedicated, weekly volunteers.
Trials and Tribulations of Fish Monitoring
- Really cold water
- Pretty quick current
- Distracting, adorable school of Coho fry zooming around
- Rain event blows out your rig!
If you spied two wader-clad individuals climbing up and down the San Geronimo Creek banks this past week, it was our biologists rescuing their fishing trap!
A fkye net is a type of fishing gear. It is a net in the shape of a bag. The bottom of the bag (net) is anchored to the bottom of a stream bed and the top of the net is suspend open.
Fyke nets are commonly used by biologists to capture coastal and euryhaline species all over the world. The system is great because it causes minimal impact on by-catch (non-target species) and is not destructive to surrounding environment.
SPAWN uses ropes and t-posts anchored to the bank to hold open our fyke net.
As the picture shows: the mouth of the net is flanked on one side by wing walls connected to the creek bank. On the other side of the net, a low rock wall extends out about two feet, stopping short of the opposite bank. Allowing stream flow around the net is an important part of the mark recapture method fisheries biologists use to assess a population. Individuals in a population have to be "voluntarily" caught. Allowing stream flow around the rig enables any determined species to swim around our fish trap. This fishing trap design does direct most of the stream flow into the mouth of the net. The water current, and all accompanying creatures, travel to the back of the net and where the rig ends with a live trap box. The live trap box is made of PVC pipe and mesh.
Every morning SPAWN biologists, with the help of some rock star Citizen Scientists, check the live trap box.
The video shows a downstream view of SPAWN's fyke net before we attached the live trap---you can see how strong the creek was flowing!
A bit about the history of SPAWN:
Salmon Protection and Watershed Network (SPAWN) is a grassroots non-profit that has been monitoring salmonid summer habitat since 1999. SPAWN began monitoring the salmonid spawning activity on the six tributaries of San Geronimo Creek in 2001 and in 2006 added springtime monitoring of out-migrating smolts. SPAWN’s efforts are meant to support and complement the work of partners in the Lagunitas Creek Watershed including the CA Department of Fish and Wildlife, National Marine Fisheries Service, National Park Service, and the Marin Municipal Water District (MMWD).
The willingness for scientists to collaborate at local, county and state levels is crucial to developing strong, uniform protection for migratory species like salmonids.
In regards to Coho Salmon (Oncorhychus kisutch), Lagunitas Creek Watershed supports one of the largest remaining wild populations. SPAWN’s objective is to measure juvenile abundance spatially and temporally throughout in San Geronimo Creek and establish a baseline for how habitat restoration efforts are protecting and improving the population.
Coho are part of NOAA's Species in Spotlight Initiative
NOAA's Salmon Recovery Plan recognizes the importance of the Lagunitas Creek Watershed to the recovery of the entire population.