Presentation Title

Evaluation of Tagging and Tracking Methods of Pismo Clams (Tivela Stultorum) in Southern California

Presenter Information

Savannah Neu, Concordia University, Irvine CaliforniaFollow
Sean Bignami, Concordia University, Irvine CaliforniaFollow

Faculty Mentor

Sean Bignami

Start Date

17-11-2018 12:30 PM

End Date

17-11-2018 2:30 PM

Location

HARBESON 6

Session

POSTER 2

Type of Presentation

Poster

Subject Area

biological_agricultural_sciences

Abstract

The Pismo clam (Tivela stultorum), a once steadily populated species native to Southern California is now potentially rebounding from a sharp depletion in their populations due to commercial overfishing in the early 1900s. The commercial fishery was banned in the United States in 1947 when the species approached local extinction in some locations. Much remains unknown about the present day life history and ecology of the Pismo clam. This initial study was performed by evaluating the feasibility and efficacy of tagging and tracking Pismo clams using metal tags and a metal detector to enable subsequent research opportunities. Five different tag types made from various metals and sizes were adhered to the clam shells and then tested for percent detection at different depths. The brass tags were found to have a higher percent detection than the aluminum and stainless steel. Additionally, the larger 19.1 mm tags were easier to detect than the smaller 12.7 mm tags. Ten clams with both sized brass tags were taken out into the realistic environment of the intertidal zone of Newport Beach during low tide and tested for detectability at depths of 10 cm and 15 cm. On average, for each depth, there was a 95 and 85 percent detection respectively. The success of this preliminary project depicts metal detection as a valuable possibility for Pismo clam tracking in the future.

Keywords: Tivela stultorum, metal, tagging, detection, clam, beach, efficacy

Summary of research results to be presented

After performing the bucket detection tests at the different sand depths, it was found that the brass tags had the highest percent detectability with the 19.1 mm tags being picked up 100% of the time up until 15 cm. The brass 12.7 mm and aluminum 19.1 mm tags exhibited very similar results to one another with 100% detection up until 10 cm. Not a single tag regardless of size or metal type was detected at 25 cm. There was an audible difference in the tone change emitted by the metal detector when the machine passed over a 19.1 mm tag as opposed to a 12.7 mm tag with the latter being much fainter.

When experimenting in the intertidal zone of Newport Beach during low tide, only a maximum of about six minutes was needed to efficiently survey the 5 m x 7 m plot of sand, with some searches lasting as little four minutes. At the ten centimeter depth, there was an average of 95% detection for the combined tag types. At the fifteen centimeter depth, there was an average of 85% detection. The clams not found using the metal detector throughout all of the trials were consistently those with the smaller size tags. The tone change in the metal detector between the larger and smaller brass tags was substantial, with the 19.1 mm tags inciting a far more apparent sound. When the metal detector passed directly over the location of the metal tag, the tone change was noticeable making pinpointing the buried clam simple.