DATA FROM THE CALIFORNIA STRANDING NETWORK

If you enter the following data into a spreadsheet, the spreadsheet can be used to generate the graphs. You may wish to print out the data tables in this section because you will have to leave this program in order to use the spreadsheet capabilities of the computer. You will also want toprint out Graph A when you make it because you will use it later to compare it to Graph E

GRAPH B Use the spreadsheet to compute the total standing of all species and compute for the given years.

QUESTIONS ON THE GRAPHS

• What years are El Niño years? Why can you determine this?
• For which species were the most stranding reported during El Niño years? During normal years? Why is this the case?
• As the population increases, the number of strandings tend to ______________. If possible obtain population estimates for these animals and test your theory.
• If species do strand based on their total population size, what would be the expected ranking for the four listed species based on their abundance in the environment? Do the statistics show this to be true?
• If you compare strandings as a percentage of the total population, how does that alter your interpretation of the data? Use the capabilities of the spreadsheet to calculate the percents.
• How does the 82/83 El Niño compare to the 92/93 event based on the numbers of animals that stranded?
• The 92/93 event was much milder and did not produce the severe storms of the 82/83 event. Was the effect on animals as great? Did the effect vary by species? Why or why not?
• Are there other events that may influence the data and its interpretation from one year to the next?

WHAT CAN BE DISCOVERED BY ANALYSIS

El Niño conditions exacerbate the rate of stranding. Below are the stranding data from all pinnipeds that stranded in the state of California during the years 1983-1996. Data are collected by NMFS based on the numbers reported to it by the members of the stranding network and other agencies. These numbers represent both animals found alive on the beach and those found dead on the beach. All dead animals are supposed to be reported, but few city agencies do this. The body is usually disposed of and forgotten. Much of California's coastline is wild and the animals that end up on secluded beaches may never found. There are two sets of data that follow. Access the data set by clicking on the link below:

Data from California Marine Mammal Stranding Network

Data from Marine Mammal Care Center at Fort MacArthur

For a more complete discussion of these topics refer to:

• Sea World Education Department Publication, The Sea World Animal Rescue and Rehabilitation Program, Sea World, Inc. , 1992

 

Activities for students:

Students can also generate graphs using spreadsheets. They especially like it if you use a 3 dimensional graphing program. I use Delta Graph for the Mac. It seems to work very easily and it looks good.

Here are some additional data that students can graph as a first experience. The data was reported from Ventura to Laguna for total marine mammals stranded (not just pinnipeds). The source is probably from the former stranding center at Marineland of the Pacific and the interim facility prior to the construction of Fort MacArthur. Make sure you graph the data first so there are no surprises.

 

YEAR # STRANDED  70 40 71 19 72 42 73 71 74 59 75 56 76 64 77 102 78 195 79 61 80 148 81 23 82 134 83 849 84 102 85 54 86 95 87 37 88 100 89 111 90 163 91 287 92 439

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