Introduction

Rapid decline of biodiversity has initiated conservation efforts to protect endangered populations, and diversity as a whole.  Protection of land, however, has some competing interests and must be planned rationally with data and clear outcomes to strive for (Cabeza et al., 2010).  The first step in this planning process is to provide quantitative estimates of biodiversity (Margules et al., 2000), one important aspect of which is determining population size trends though time.  This can also serve as a goal of conservation efforts if the species has a downward trend through time, with the goal being stabilization of population size.  For species that are not endangered, population dynamics studies can still be useful as a tool for guiding other conservation efforts.

The turban sea snail is a gastropod inhabiting the rocky intertidal zone from Vancouver Island to Baja California (Walker and Carlton 1994; Morris et al., 1980).  The population of turban sea snail is densely populated in these tide pool areas, so finding a method of estimating the population size is necessary to observing dynamic trends though time.  Though not considered to be an endangered population, sampling populations such as these could aid in other conservation efforts, such as a new field of ecological engineering.  A perfect example is shown by Firth et al., 2014, where measurements of population dynamics in different intertidal environments were used to promote the use of barricades and barriers made of natural rock simulating material (Firth et al., 2014; Chapman and Blockley, 2009; Browne and Chapman, 2011, 2014; Chapman and Underwood, 2011).    Our study will look to provide a robust population estimate with narrow confidence intervals, and compare the population size of tegula funebralis over a 2-week time period in the rocky intertidal zone near Morro rock utilizing area based sampling methods.  

Data Collection- James

We went to the morro tide pools to sample the turban sea snails with some twine marked in 1 meter increments.  When we first did our pilot study, we considered the use of fixed width transect sampling, however the density of the snails was so large that we decided transect sampling was a more achievable method.  We were planning to use the twine to both outline the edges of the study area, and to make a 1m2 quadrat for sampling.  This method was surprisingly successful at directing us to our randomly assigned quadrat locations.  Upon choosing the first quadrat, we quickly figured out that the area of each quadrat was too large, as there were over 100 individuals in the first sample.  We reduced the area of each sample to a quadrat with sides 0.5m, and an area of 0.25m2.  This quadrat size was much better, and the rest of the sampling went smoothly.  We went to sample at the time projected to be low tide, and we were able to sample with no difficulty from the tides until our last sample.  Another sampling day will be planned for next week to compare the population estimates.

Data Collection

Data collection has been a learning experience for our group so far. We went to Montana de Oro one afternoon this week where we spent a few hours looking for snails in between the rocks close to shore. We brought a length of twine with us onto which we marked off multiple meters. This twine helped us determine the location of the quadrats on the beach that we used a random number generator on my phone to come up with. As a group we decided that we would work with quadrats that could range from 20 meters into the water, and 50 meters down the beach. Once we located our first quadrat out on the rocks we made our 1x1 meter square and counted the snails present. We came up with about 140 snails and decided the size of the quadrat needed to be smaller; a .5x.5 meter quadrat was the most logical step. This was one part of the data collection that we tweaked to make collection easier. Once the size of the quadrat was adjusted, collection went more smoothly. The final thing we learned that day was that checking the tide was essential to our success. As we neared the end of day we noticed the water level getting higher as the tide came in. This was when we learned for our next day of data collection, checking the tide was a must. Besides those few tweaks everything went smoothly out at the beach and should go even better the next time we go out.

A Snail's Pace Pilot Study

As a group, we hope to observe and estimate the population of tidal snails in Morro Bay over time. Snails are mainly land animals, but require a great deal of moisture to survive. Thus, many in the central coast of California have adapted to thriving off the tidal zone. We will conduct a pilot study to estimate the population of snails around Morro Rock at one time point and hope to follow up a week later with another population estimate how much the population varies over a 1 week period.

Methods:
We will survey the area around Morro Rock at the lowest tide of the day. Using a geographic map of the area we will divide the area into 1m squared sections. After taking random samples with a quadrat, we would use simple statistical techniques to create a 95% confidence interval for the actual population of snails. The snails will not be handled, manipulated, or the environment disturbed in any way. We will also take time to examine other coastal sites in Morro Bay and Los Osos for extensions or replacement of population estimates as backup.

Morro Rock. Picture by Kelsie Clausen