Green Crab Male to Female Ratio 2013 to 2017

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Alaina Holmes
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1 Green Crab Male to Female Ratio 2013 to 2017 Arianna Baker Bath Middle School Bath, ME Mrs. Wright 12/19/2017

2 Abstract In our green crab study we looked at the population of green crabs. We also looked at how the clam population is decreasing. For our study we used legal crab traps. We also decided to use the catch and release method. Two of the charts I made were similar. The other chart I made had drastically more male crabs than female. In the studies that were done I found that there were drastically more green crabs than any other crabs in our ecosystems. I also found that the native crab population has decreased. Introduction In Maine, invasive species are taking over. The one that has really taken over is the green crab. The clam is being affected by the crab. As well as the clammers that have been clamming for many years and rely on that job as their main or only source of income. Chad Coffin, a clammer from Freeport said, When I first started clamming in 1990, there were three wholesalers here in Freeport. It is down to one now. In 2016 clam landings declined by 21 percent they used to produce 9.3 million, but now only produce 7.3 million. The green crab is very bad for our ecosystem because they eat clams, mussels, eelgrass as well as other small crustaceans and mollusks. Green crabs are from Europe and reached Maine in the late 1800s early 1900s. They are also bad because they crowd out the native crabs, ruin the biodiversity, and eat the native crab s food. By doing these things it stresses out the native crabs. Green crabs are adapting by mixing with native crabs and because the ocean temperature is rising they can live easier in our waters. This is making them stronger and harder to get rid of. The crab trap study we did is a way to gather more evidence about what is happening to our ecosystems. The study shows us just how many green crabs there really are it also showed that there are not many native crabs left. I know this because we found many more green crabs than native crabs. Using the crab traps is very easy. They sit in the water for a period of time and the crabs go into the traps because bait is put into them. Because of this they are better for studies because it s easier to get a lot of crabs for your data.

3 Methods We used the catch and release method which is when you catch something without injuring it then you release it back into its habitat. We did this at Todd s Landing and Reid State Park in Georgetown, Maine. We went there because we had been doing that experiment at those same spots for a long time. Another reason we went there was because many crabs live there. We used legal crab traps throughout the entire week. If there was any other wildlife in the traps we would release it right away. The traps were set on 10/23 / 2017 and used sardines in oil as bait. On Tuesday, we took them out of the water, emptied them, and put the crabs into a bucket. We next marked them with insta-dry nail polish and released them. On Wednesday, the traps stayed in the water because our trip was cancelled due to the weather. Thursday was a repeat of Tuesday. On Friday, we emptied the traps once again, but instead of putting the traps back into the water we took them back to school. The way we measured the crabs was by putting a ruler across the carapace on the last spine. By doing this we were measuring it at the widest part of the crab. We used the centimeter side. Next, we recorded the measurements on a sheet. We also recorded if the crab was male or female. Among other things such as color and if they were marked with nail polish.

4 Results In this pie chart from 2013 to 2017 at Griffith s Head there were only a few more male crabs than female crabs.

5 In this pie chart from 2015 to 2017 at Todd s Landing it shows that there are drastically more male than female green crabs.

6 In this pie chart from 2015 to 2017 at Fort Popham it shows that there are only a few more female crabs than male crabs. Conclusions The Bath Middle School 7th graders found that there are more green crabs than any other crabs in our marine ecosystem. This was very concerning to us. They have been doing this study since They found that the green crab population rapidly increased since the study was started. They also learned that the native crab population has decreased. Because the green crabs are taking over the marine ecosystem the native crabs are very stressed out and there isn t many of them left. I learned that because the native crab population is decreasing it makes it so there isn t a lot of crabs for humans. Green crabs don t have a lot of meat which means humans don t eat them. Green crabs are impacting our ecosystem greatly and hurting the biodiversity as well as many other things. My data shows that at Griffith s Head from 2013 to 2017 out of 312 green crabs 58 percent of them were male and 42 percent of them were female. I also made a graph for Todd s Landing and out of 221 green crabs 23.1 percent of them were female and 76.9 percent of them were male. This showed that from 2015 to 2017 there were many more male than female crabs. The last chart I made used data from Fort Popham

7 starting in 2015 and ending in There were 56.1 percent of female crabs and 43.9 percent of male crabs. All three of these charts are different. The chart from Griffith s Head had almost the same number of male and female crabs, but there were more male green crabs than female. In the chart from Todd s Landing there were many more male crabs than female crabs. The chart from Fort Popham was a lot like the one from Griffith s Head, but instead there were more female than male crabs. I found this data very interesting because two of them both almost are the same with male and female almost being equal. The another chart has way more male than female crabs. I think there is some sort of pattern with the charts. To make the studies better we could of made all the spreadsheets with the same format.the way we could do this is by when you put the information in the spreadsheets make sure that the data is lined up. Also have the data for male and female all be uppercase because if you were to make a graph you wouldn t have to go through all the data and change it. The reason I would do this is because when some of the data is uppercase and some is lowercase the graph has 3 or 4 sections instead of 2. The last way we could make using the spreadsheets better is by spell checking everything and making sure there aren t any empty columns in between the data because this messes up the number of data when making charts. References Hentz, John; Shellfish Warden, Georgetown, ME, Lesson, Sept Indrick, Ruth; Kennebec Estuary Land Trust, Project Coordinator, Expert during field work, October 2017.

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