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Studying The Movement Of Fish

Published: June 1, 2015

CSULB Marine Biology Professor Chris Lowe and his students are studying whether Southern California Edison’s (SCE) mitigation reef produces fish biomass as required by San Onofre Nuclear Generating Station (SONGS) operating permits, or simply attracts fish from nearby natural reefs. The grant funding the project is for $279,000.

“This is for us to study how fish use the largest artificial reef built in the country,” said Lowe of the Wheeler North Artificial Reef, which covers 174 acres off the coast of San Clemente. “As part of its mitigation requirements for SONGS’ operating impacts to the marine environment, SCE, working with the California Coastal Commission (CCC), put in this large artificial reef.”

Built of quarry rock, the artificial reef is less than a half mile from natural reefs beginning at the San Clemente pier and going south. The CCC implemented the SONGS Marine Mitigation program in 1997 and the construction of the reef took approximately a year, being completed in 2008.

“This is a permit condition from the California Coastal Commission,” said Kim Anthony, a senior biologist and environmental project manager at SCE, who is a former graduate student of Lowe’s. “It allowed SONGS to operate under this mitigation condition, so that’s what we’re doing with this reef.”

Some believe that artificial reefs/habitat do nothing but draw fish from natural habitat, which in turn would mean it’s not producing new fish, but rather depleting natural habitats. The other side of the argument is that artificial reefs actually help produce fish and the fish biomass increases.

“We know they are reproducing on the reef, so it looks as if they are producing more fish,” said Lowe. “We know fish are coming to this reef from other places, but the part that’s been missing is the movement part and that’s why SCE came to us. My lab specializes on where fish go.”

CSULB graduate students Ryan Logan and Caitlin McGarigal are in the field, responsible for tagging and tracking the fish with the aid of acoustic receivers placed around the reef.

“Essentially what I am doing at Wheeler North Artificial Reef is tracking the movements of kelp bass, barred sand bass, and California sheephead within and around the reef,” said Logan. “The information I am collecting will have local and potentially global implications for other artificial reef projects, environmental policy and proper management of artificial reefs.”

“By using our acoustic array, we can determine if fish stay (on the reef) or if they move,” said Lowe. “So we can start to look at movements to determine whether these artificial reefs are really producing fish or simply attracting them from other places. More importantly, since this is one of the best studied rocky reefs in the world, we can begin to understand under what conditions fish caught and tagged at the reef may leave. This will help us better understand what fish are looking for as a good home.

“The piece that’s really been missing has been about production and are fish staying there or simply passing through, eat a few meals and then take off?” added Lowe. “Previous studies of fish populations there are really just snapshots in time, but because the fish being counted are not marked there is no way of knowing if they are the same fish.”

By coupling previous studies with Lowe’s movement study the question as to whether artificial reefs produce fish or simply pull them from natural habitats can be addressed.

Both McGarigal and Logan are working toward master’s theses associated with this project. Their job, according to Lowe, has been to deploy acoustic receivers around the reef that are constantly listening for fish surgically fitted with acoustic transmitters. When a tagged fish is within 300 yards of a receiver, it records the transmitter ID number, date and time the fish was there. There are strings of receivers oriented perpendicular from the shoreline between the artificial reef and neighboring natural reefs. Fish are then caught and then tagged with an acoustic transmitter. The $400 transmitters last about a year and allow the fish to be tracked. According to Lowe, the goal is to tag 160 fish.

“The technology is very expensive,” said Lowe, “but it enables you to answer questions you cannot answer any other way.”

Once the technical aspects are in place, it’s really time on the water—lots of time.

“My students spend thousands of hours out on the water fishing, tagging and maintaining the acoustic receivers and downloading information, so our partnership with recreational fishers and party boats are key,” said Lowe. “My students can be onboard and any fish the fisherman don’t want they can tag and put back in the water.


“The great thing about this partnership is that there are several components to it,” continued Lowe. “One is the other graduate students looking at what happens to fish caught in the reefs. We’ve piggybacked this project with another question and that is, ‘What are the physiological and behavioral effects of a fish being caught and then released?’”

To determine that, a small blood sample is taken from a fish and its stress level from capture and handling can be accessed. Then, that fish is put back in the water and when recaptured a second blood sample rapidly taken and its physiological state before being recaptured can be determined allowing researchers to tell if a fish is back to normal physiologically.

“It is important to understand how capture and handling stress might impact growth, reproduction and, ultimately, population sustainability, especially for species that are subject to frequent catch and release,” said McGarigal. “Ryan and I have been collaborating so that I take blood samples from the same fish Ryan is tracking in his movement study. Analysis of certain chemicals in the blood will allow me to determine whether and to what extent these fish are physiologically stressed from the capture and handling process, and by analyzing a second blood sample at a later date I can determine how long it takes fish to recover.”

Ultimately, McGarigal predicts there will be almost 100 percent post-release survival for these species and observe a full physiological and behavioral recovery within 24 hours.

“These results will benefit recreational anglers by providing actual data supporting catch and release as a viable management strategy,” she said, “and I will be able to identify and educate the recreational fishing community on angling and handling practices that minimize stress on fish, and thus cumulative impacts on the population.”

“That information becomes really important for sustainable fisheries,” said Lowe. “The part that’s really cool about this project is that the graduate students are working side by side with fishers, who in turn are learning about how this science can keep them fishing.”

Five main groups will benefit from this research—local companies and agencies with an interest in the artificial reef, national and international coastal resource managers and entities needing to mitigate impacts on coastal marine resources, scientists studying the function of artificial reefs, private groups advocating for the construction of artificial reefs, and scientists and natural resource managers interested in movement patterns of reef fishes.

“I see this outreach, this kind of fisher education going hand-in-hand with the objectives of SCE with this artificial reef,” added Lowe. “They put that reef in place so fishers would have more opportunities and the goal of our research is to insure that those opportunities continue and grow.”

“This is a big, exciting project with a lot of challenges,” said Anthony, “but Chris and I are really hoping that the results of this study will be a key component to answer a lot of questions that still need to be addressed. Once the students collect the data we can start to combine those data with what’s already being collected on the reef and get a better picture of what’s actually going on with the ecology of the reef.”