The Salmon Protection and Watershed Restoration Network (SPAWN) believes recent vandalism to a trap box and fish net in San Geronimo Creek that may have resulted in the death of endangered coho salmon and steelhead trout likely stemmed from community anguish over pending streamside development restrictions that the organization has aggressively promoted.

A video surveillance camera used to track fish and wildlife activity caught the vandal’s blurry image on the evening of May 14 pulling the trap box from the stream. The nonprofit advocacy group had another trap box in place within 24 hours, and announced it is offering a $500 award for information on the individual caught on tape.

“This is somebody that doesn’t have the courage of his convictions to confront us,” Andy Harris, managing director for SPAWN, said of the vandal. “I think this individual was some fringe nutcase acting on his own” rather than part of a coordinated effort to intimidate the organization. Mr. Harris declined to comment on whether or not there are leads on the identity of the vandal, whose damage totaled about $1,500. If the individual is found to have killed an endangered species, which Mr. Harris believes is likely the case, fines or even jail time could await him or her.

The system, one of three that SPAWN says catches about 60 percent of the federally listed fish swimming through the creek, uses a net to funnel the fish into a trap box, where young fish known as smolts are counted and measured before being released to continue their pilgrimage to the ocean.

The equipment was installed in March and scheduled to be removed in June, in the first year of a three-year study on coho and steelhead during the spawning season.

Mr. Harris said there is a strong possibility that the individual’s motivation was seated in ongoing and heated debate over a proposed stream conservation ordinance that would require homeowners to obtain varying levels of permits to build on their property.

He reported that there have been instances of verbal assaults launched by drivers passing SPAWN’s offices in the former town of Tocaloma and said last winter the group’s executive director, Todd Steiner, and his family were personally threatened. Several months ago at least one poster referencing Mr. Steiner and his residence was placed in a local post office.

“Passions are so highly inflamed around this issue,” Mr. Harris said.

Tensions between SPAWN and homeowners in the San Geronimo Valley stem from SPAWN’s legal efforts to push the county to implement an expanded stream conservation area (SCA) along streams in Marin, including in the valley. The county has spent close to $300,000 in legal fees to fight lawsuits brought by the group.

The expanded SCA would require homeowners to obtain permits to add development to properties, with some exemptions. An expanded ordinance is required under Marin’s 2007 Countywide Plan, and SPAWN took legal action when the county did not act on them.

Last fall a court approved a moratorium on development in the SCA until new ordinances were implemented. A board of supervisors hearing on the expanded SCA is scheduled for June 18.

Both homeowners represented by a nonprofit group, the San Geronimo Valley Stewards, and SPAWN expressed disapproval of the draft ordinance at a planning commission meeting in May. Still, Mr. Harris believes some of the tension will die down after the new ordinance is in place because it will remove the uncertainty surrounding the issue.

Peggy Sheneman, a director of the San Geronimo Valley Stewards, which advocates for the rights of homeowners in the area, said it was a “terrible thing to happen” and condemned the action, but added that “you don’t make a lot of friends” by calling people “so-called property rights activists,” the term used in SPAWN’s press release.

“I think that people are very angry at SPAWN’s litigation approach,” and “feel bullied,” she said, adding that she could not imagine any homeowner in the valley vandalizing the equipment, as they care about endangered fish and the health of the watershed.