Results & Conclusion

Our results indicated that the population estimate is around 99,800 individuals with a 95% confidence range of 95,616-103,985 individuals in the 1000m^2 area. This results in a density of 25.15 individuals per meter squared. While taking the data, we realized that it would be impossible to gather an entire census, as the population is so dense and environmental factors such as the tide would limit our abilities. This method was the best way to go. If we had used a transect model, the data would have been skewed, as the population density was not equally spread over the sample area; there were less snails present on the rocky shore than in the tide pools, and the most directly in the surf edge.
The population estimate method we employed could be easily used for many other locations in Montana de Oro State Park, Morro Bay, and even along he coast of California. These methods could also be utilized over time to provide an accessible understanding of the population dynamics of the Tegula funebralis Gastropoda snail. Although the turban sea snails are not endangered, using their population dynamics model, data could be extrapolated to draw inferences on populations both interacting and depending upon the turban sea snails. They could also be used in conservation efforts to provide sanctuary to other endangered species.

Table 1. The actual counts of the individuals found in each of the 20 quadrate sampled.

Table 2. The statistical data of the population estimate generated from the mean of the individuals from Table 1 and the study sample area of 1000m^2.

Methods

To estimate the population size of turban sea snails in the study area, we used quadrat sampling.  A spool of twine was marked at every meter, and a random number generator was used to select the coordinates of the quadrats sampled.  The twine was used to measure the study area (20 meters x 50 meters) and locate the coordinates of each quadrat, then the twine was formed into a square with 0.5 meter sides to sample.  All individuals were counted within the 0.25m² quadrat, with those on the edges counted in the quadrat if they were more than halfway in the sample.  A total of 20 samples were taken over a period of 60 minutes to ensure a closed population through the data collection. 

Tide pooling!

Wednesday we went out to turn our pilot study into a real experiment. We opted for the tide pools in Montana de Oro state park, as they seemed more accessible and feasible for our study. We walked down to the bluffs by the Badger trail. I measured the total area to be around 0.15mi in length by running as close as I could on the perimeter. The tide posed an issue of width, but we went out as close to low tide as we could, and it seemed to be minor while sampling. Measuring the length in meters by twine proved simple and effective. The random number generator gave us coordinates along our twine axis and then further down our width axis. From the point on the horizontal twine, we walked out to various points to set up the quadrat. With an incoming tide obstructing the view and changing the environment, we opted to only count 10 quadrats 0.5m squared. We counted as fast as we could, but in the end it is only an estimate. We have to acknowledge that there is a probability of detection involved; not all turban snails could have been seen or present. I would call it a successful sample because the random number generator spread our samples over a wide variety of spots in the area, and the data seemed cohesive.
- Kelsie Clausen

Here are some photos I took of the day:

The study area

The turban snails counted

Tide pools stretched longitudinally

A typical view of a quadrat sample

Marking the twine in meters

Counting the distance horizontally

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