Catarina Pien



I graduated with a B.A. in Biological Sciences from Wellesley College in 2010. During my undergrad, I interned at the University of Delaware (summer REU) with Barb Campbell, investigating the usage of 16s rRNA abundance as an indicator of marine bacterial abundance. At Wellesley, I studied invasive plant species in Lake Waban, and the following semester studied abroad in Panama, which concluded with an independent research project. I conducted a study comparing mangrove and mangrove fauna density at different sites. I continued researching mangroves in Utila, Honduras that summer, investigating the difference in fish density close to, and away from mangrove roots.

After graduating Wellesley, I studied in Taiwan for a year to improve my Chinese, then returned to my hometown in New Jersey, interning at the Marine Mammal Stranding Center in Brigantine, NJ, and volunteering in the Ichthyology department at the  Academy of Natural Science in Philadelphia, helping catalog, research, and photograph neotropical freshwater fishes.

I started at MLML in 2012, and am currently working on my thesis (see below), and as the museum student assistant for the MLML museum, where I am organizing, cataloging, and photographing the fish, invertebrate, marine mammal, and bird collections.


Changes in the Elasmobranch Assemblage of Elkhorn Slough, California


Cat Pien with a Leopard Shark (Triakis semifascata)

Elkhorn Slough is a 1,200 hectare elongate estuarine embayment located in Moss Landing, Californiaand is the third largest estuary in California. Over the last 150 years, agriculture and increased coastal development altered the structure and natural evolution of Elkhorn Slough. In 1946-47, Elkhorn Slough underwent one of its most significant anthropogenic changes when the Army Corps dredged a channel for the construction of Moss Landing Harbor. The alteration opened the slough directly to Monterey Bay, transforming it from a depositional to a strongly eroding, saltwater-dominated estuary.

Elkhorn Slough National Reserve; photo credit: Friends of Pajaro Dunes

Elkhorn Slough National Reserve; photo credit: Friends of Pajaro Dunes

Elkhorn Slough provides habitat for several elasmobranch (sharks, rays, skates) species. Some of the species that have historically been common include Leopard Sharks Triakis semifasciata, Bat Rays Myliobatis californica, Round Stingrays Urobatis halleri, Gray Smoothhounds Mustelus californicus, Brown Smoothhounds Mustelus henlei, Shovelnose Guitarfish Rhinobatos productus, and Thornback Rays Platyrhinoidis triseriata


The Thornback Ray P. triseriata

In this study, I will survey the elasmobranch assemblage in Elkhorn Slough over the course of 1.5-2 years, externally tagging species, recording sex, total length, maturity, and collecting GPS coordinates, fin clips, and oceanographic data. I will use the collected data to describe the variables (e.g. salinity, temperature, turbidity) that correlate with elasmobranch presence, examining patterns between species, sex, and maturity level. I will also examine the relationship between historical changes in the Slough and changes in elasmobranch assemblage.

My three main objectives are:

1) to quantify the current composition of elasmobranchs that either permanently or transiently reside in or occupy Elkhorn Slough

2) to compare the results to data collected from the past few decades. Past records consist of data from shark derbies conducted between 1951-1995, as well as a variety of studies conducted through MLML and other institutions (1964-2014).

3) to study life history characteristics of P. triseriata. Life history data on P. triseriata is not only lacking from Central California but is virtually nonexistent throughout its range. In the last decade, the abundance of P. triseriata has notably increased in Elkhorn Slough, and multiple gravid females have been collected. It is possible that environmental modifications, due to changes over the past several decades to Elkhorn Slough, such as increased saltwater influence (salinity), habitat alteration, and/ or changes in prey and competitor abundance have created suitable habitat for the rays such as has been observed for T. semifasciata.

Anthropogenic impacts are perceived to result in decreases in biological abundance and diversity, but not all changes are necessarily negative for all species. It is possible that the structural and environmental changes in Elkhorn Slough have impacted habitat and estuary conditions to the benefit of certain populations, such as P. triseriata. Collecting more information about P. triseriata will provide a starting point for understanding the recent increase in species abundance, and for managing the species along the Eastern Pacific coast.

Data collected for this proposed study will provide a baseline for future studies, with standardized sampling methods that can be replicated in the future for measuring the elasmobranch populations in Elkhorn Slough, and will inform estuary and Thornback Ray management by exploring the influences of the natural changes, human development, and subsequent restoration and protection efforts on an estuary, specifically on the assemblage of top predators in the estuary.