The die-off mirrors a similar one in 2006. An emergency response team is investigating the cause.
By Melonie Magruder / Special to The Malibu Times
The Resource Conservation District of the Santa Monica Mountains will be meeting this week to discuss its rapid response team’s effort to solve the mystery of the recent sudden decline in Malibu Creek’s fish population, a phenomenon that appears to mirror a similar event three years ago.
In 2006, all the visible aquatic life in Malibu Creek between Rindge Dam and Malibu Lagoon died during a three-month period. At the time, conservation scientists attributed the die-off to a combination of high water temperatures, reduced dissolved oxygen, low water flow from the Tapia Water Reclamation Facility upstream, algal growth and the smothering presence of decomposing diatoms (microscopic, one-cell alga).
But toxicity studies weren’t performed until long after the fact, conservation district spokeswoman Rosi Dagit said. Since then a rapid response team was organized to hit the field and find immediate answers in the event of a sequel.
“Fortunately, the fish population of Malibu Creek [including the endangered California steelhead trout] came back naturally,” Dagit said. “In fact, in 2008 we counted the highest number of trout we’ve seen since we started keeping records. So what has happened between then and now to cause the population to plummet? That is the question we are trying to answer this week.”
The RCDSMM rapid response team includes specialists in toxicology, water quality and habitat restoration from a range of state and federal agencies.
Creek surveys are conducted using both bank-side observers and underwater snorkelers; and data is accumulated for species counts, water levels and temperatures, bacterial contamination levels, range of dissolved oxygen and the presence of toxins.
“We had never observed the dramatic rise in the general fish population that occurred between 2006 and 2008,” Dagit said. “The $64,000 question is why? With this current die-off event in progress, we can figure out what it isn’t and what it is, and maybe prevent such an event in the future.”
Steelhead trout live most of their lives in the ocean, returning to their home creeks in early spring to spawn. The young stay in the creek a few months until big enough to travel and head downstream for the ocean around May.
Because of urban sprawl and habitat degradation, Southern California steelhead trout populations have declined so precipitously that Dagit figures there are perhaps as few as 500 adults of this steelhead species left in the wild (there are hefty $25,000 fines for taking steelhead trout from Southern California watersheds, she said).
Dagit suspects the recent decline is due to similar reasons as those in 2006.
“The most important thing is for us to come together and determine what tests must be performed, what management strategies must be developed so that we can prevent this from happening again,” she said.
One barrier to restoration of Malibu Creek and all its fish populations is the 83-year-old Rindge Dam, constructed three miles up the creek from the lagoon to provide a water supply for May Knight Rindge’s family and livestock in the 1920s.
The 100-feet-high, 140-feet-wide dam lost most of its function by the 1950s, due to a gargantuan accumulation of sediment, and was decommissioned in 1967.
The controversial efforts to remove the dam and restore the creek’s natural flow and habitat have been ongoing for years. The U.S. Army Corps of Engineers and California State Parks have been engaged in a nearly $4 million study of the dam’s removal and estimates on the project have ranged from $31 million to $72 million, according to earlier coverage of the issue by The Malibu Times.
Some people, including Ronald L. Rindge, descendent of May Rindge, are opposed to the removal of the dam, saying it would be a waste of money and that the conditions of the creek are not suitable for restoration of the trout, which, he has said in the past, is not necessarily native to the creek. Rindge has claimed the trout were planted as game fish early in the 20th century.
Nevertheless, plans have continued for the study to remove it.
Jim Hutchison, watershed studies group leader of the ACE, said he has worked with a multi-agency group, including local stakeholders, to develop an interim report and recommendation plan for the fate of the dam.
“We are addressing issues we feel are vital to the continuing health of the Southern California steelhead trout species and have come up with a general recommended plan,” Hutchison said. “Unfortunately, we are in a holding pattern because matching funds [of approximately $150,000] from the state parks system to complete the study have been cut off.”
Hutchison said the plan tentatively recommends removal of the dam and accumulated 780,000 cubic yards of sediment, restoration of habitat around the dam and smaller changes to other upstream barriers like culverts and bridges.
“Removal of the dam and restoration of the creek flow would open up another five miles of stream habitat,” Hutchison said. “It’s easy to focus restoration efforts on spotlight species like steelhead, but this move would benefit several species up- and downstream, including large mammals, plants and other aquatic species.”
Hutchison emphasized that initial estimates for costs and feasibility are preliminary, and require more analysis and vetting from the public.
Elements that affect cost are transport and final disposal of sediment and concrete, but local construction companies could be invited to bid on the project, benefiting local economies.