Saturday, July 26, 2014

Catherine Zhang -- Assignment 2: why the snail shells are near the shore?







So from the shore of Lovells Island we explored, we found that there is a piece of huge white stone by the sub-tidal pool. We found several colorful snail shells on the surface. These shells are totally empty, and the areas near the umbilicus are broken. But we couldn’t find any other similar snail shells on the shore. Interestingly, on the way back to the boat, I found there are lots of similar broken snails under the bushes and trees. And I also found a live snail on the back of a leaf. Here are the questions: what are these snail species? Why some of them ended up near the shore since there are lot more under the trees?
            To find out the answers, I went online to search for “Boston Harbor Lovells Island snail shell” and it took me back to several posts in this blog both 6 years and 4 years ago (again…). From previous student’s observation, these snail can be 3 types of snail species which are white-lipped snails (Helix albolabris) or brown-lipped snails (Cepaea nemoralis). With doubt, I looked up both snails and found out they do look like the ones I found on the island. Although Brown-lipped snails are native in Europe, they were introduced to North America. And White-lipped snails are also native in central Europe and Western Europe until they were introduced in Northeastern America. 

            Now the question is why these empty broken snail shells are near the shore? I personally think that is natural force. The wind and water cannot bring only 4 snail shells from other places to the shore since I saw much more shattered shells under the bushes which are far away from the shore (unless there is a storm which brought only 4 shells to the shore. That sounds impossible.). I think they are brought here by other species. But with observation, I realize that all the shells are opened on the umbilicus as same as the ones I found under the bushes. I guess its predators ate them and left them on the rock. To know what species may eat snails, I looked up “land snail predators” and it comes out species of invertebrates, amphibians, reptiles, small mammals and birds. But the area with snail shells is just by the shore, there is no plant. It means the snails didn’t crawl all the way from woods and eaten by other species, which means some species brought them there. It is impossible for invertebrates, reptiles and amphibians to drag them all the way down to the shore. So it must be small mammals or birds. From the article “Snail Predators”, it says mammals such as the mice, shrews and birds will eat snails. On the other hand, I learned there are no mammals (except rangers) on Boston Harbor islands. So now we finally focus on the birds. From my own knowledge, I know big birds save their times by just swollwing the whole snail. But since the snail shells are broken on the almost same side, I think the birds use their beak to break through the shells and drag out the snails. So I looked up “small birds eat snails”. In the article “What kinds of birds eat snails,” it says songbirds such as song thrushes can eat snails by smashing them on rocks. So far, I think thrushes brought the snails to the huge rock near the shore.


PS: Pictures below are all from posts which are 4 years ago and 6 years ago. From the snail picture 4 years and 6 years ago, there were a lot of live snails, but last time we went to the Lovells Island, we only found 3 live snails and rest of them are only shells. I just wonder if it is because of human distraction, weather, temperature (4 years and 6 years ago the snails were found half a month later than this year ), birds and other reasons.....



Catherine Zhang -- Field Trip to Lovelles Island Assginment 1: Drawing and Naming

            Last Friday, we went to the field trip to the Lovells Island. It is a fairly small island which is smaller than the half size of Long Island. It is on the east side of Boston Harbor. We took a private boat behind the Barking Crab Restaurant and go to the island. The boat owner is Charlie, nice awesome guy who has been living on the boat for 4 years. From Charlie’s introduction of himself, I know that he and his wife own the boat, does wedding, festival celebrating fishing and other things on the boat to make a living. He also told us this year’s water is colder than last year, on Friday it was 56 Fahrenheit.
The weather on Friday was sunny and windy on the boat. Around the time of 10:30, the tide was coming up, because you can see in the picture, the wood fences near our boat shows it has 8 visible pieces fences we can see. Charlie showed us the top two pieces are dry and clean which means they probably never under the water. The third piece is mostly covered by fresh green moss which means it always reached by water but it barely goes under the water. But the 7th piece which is next to the water has a lot of seaweed growing on it. It means that it has its most time under the water every day and water plants even grow on it. It means at that moment the water was low and the tide was coming and the fences would be covered by water.
As soon as the boat started, Bruce, our professor, started to tell us that we will catch some fish and observe them, and then we will go to the Lovells Island. He first showed us sea worms, which are grate bait for fish. After research, I found that the sea worms are Clam Worms (Nereis Virens). This type of huge nasty worm can be as long as 21 inches and 0.5 inch wide. It has long round bodies with many tiny orange legs (Parapodium) on the side. Its back is dark green as beneath is light red or orange. It has so many segments that I can’t count. From the guide book, it says it has 200 segments! It usually stays in sand or mud on the bottom of protected water or brackish estuaries. Interestingly, this worm bites people since it has tentacles, mouth and black jaws; we can see it twists its body and uses its mouth to bite the person who is holding it. 
 

On the way to the Lovells Island, we stopped at one area and used the clam worm to fish. The first fish we caught was a Black Sea Bass (Centropristis striata). It is about 15 inches long. It is mostly grey with beautiful blue or green color on the top of its spine. It has sharp striped dorsal fins which are almost connected to the caudal fin (black with white spots on it and white edge). It also has one pair of anal fins and a pair of pelvic fin and pectoral fins. Its upper lip is dark blue or grey as the lower lip is white.  It is very surprising that sea basses are born as girls and later in their years they will turn to boys. The first black sea bass we found is just about turning female to male. From the website of NOAA (National Oceanic and Atmospheric Administration), I know black sea bass are omnivorous that it feeds on invertebrates, squids and other smaller fish. I also caught a black sea bass. But because it hasn’t reached its maturity, I had to release it.
Then my classmates caught another type of fish. There are two of them; the smaller one is about 12 inches long and the bigger one is about 16 inches long. It is round and flat with light green scales and a red fan-shaped tail. It also has even fins on the edges. The fish is really odd that it has only one side filled with scales and brown spots, and other pinky-white side is smooth without any scales. But the eyes are both on the scale side of the fish, and its mouth opens on the left side of the body. I think it means the fish usually stays on the bottom of the sea as it swims sideways when it can be aware of other living things above it. After searching the NOAA again, I realize that the bigger fish may be the Yellowtail Flounder (Limanda ferruginea) and smaller fish is Summer Flounder (Paralichthys dentatus) because we can see in the picture that the bigger fish has brighter, red color and less spots than the smaller fish which has more dark brown areas on its body. Flounders feed on smaller fish, different types of sea worms and crustaceans.       
Also my classmates caught two smaller fishes of same type and they are about 8 inches long. It has a huge mouth which compares to Flounder’s mouth or Black Sea Bass’ mouth. Its body is really thin. It also has huge eyes with a yellow circle outside and a black eye ball inside. On the upper part of its body, it is grey with dark brown spots on it; the color started to fade while getting close to the belly and finally it turns out to be silver-colored. Its tail and fins are dark grey or green. So also from the NOAA website, I found this type of fish is Silver Hake (Merluccius bilinearis). It is interesting that the Silver Hake usually stays on the bottom of the sea which is sandy, muddy during the daytime and comes out during midnight to feed on semi-pelagic predators.
The final fish species we had caught is the Atlantic Striped Bass (Morone saxatilis). As soon as I saw the strips on its body, the big belly, long and huge size of it, I know it is Striped Bass. From the professor, we know we cannot keep the striped bass shorter than 28 inches. So when the TA caught the striped bass which is 23 inches, she had to put it back to the ocean. But when another classmate finally got the one which is 38 inches long, we kept it! That Atlantic Striped Bass is so beautiful and huge. It is almost as long as a human being and I think there is no problem that a fist can fit in its mouth. The upper part of the fish is dark grey or green with black strips all the way down as the background color fades to white.

Since we were still having class and our mission is to get the Lovells Island, we had to stop fishing and leave. The island is one of the Boston Harbor Islands and a national park area. It is long and round shape with a lot of greens on it. The beach is rocky instead of sandy. As tides come in and go back during different time period of the day, the shore forms up different tide pools as they are tiny pools as tides come in and then dry out as tides go down. On the island, we also found many different species in these tide pools near the shore. 照片
On the way to the tide pool, we saw the wrack zone between the land and the ocean. It is the place where the highest tide hits the beach. We saw just by the ocean, there are rocks, sand, dry seaweed and then grass by orders. The dry seaweed was brought up by the tide and left on the shore. 
First thing I found here is something looking like sea snails. This soft creature is living in the dark brown or grey spiral shell with waves along it. It is about 0.8 inch. The inside body structure of the snail is as same as one snail we see in the garden. But in additional, it also has a piece of operculum which protects it from drying out or being eaten by other predators. I found them all over the rocks in the saltwater in the pools. After I looked them up, they are actually Common Periwinkles (Littorina littorea). From the Hichhikers' poster, it says it has"shells usually dark, transverse black stripes on tentacles, poorly developed sutures on whorls"They feed on diatoms and algae which attach on the rocks. 
On almost every rock, I saw a lot of barnacles. these barnacles are much smaller than the ones we found on the blue mussels near the Fanpier area. Most of these barnacles are same size and they almost connect to each other. I think they are Northern Rock Barnacle (Semibalanus balanoides) since the pieces of plates are too many to count for me. Since I didn't take a picture from it, I searched online about "boston harbor lovells island barnacles" and one good picture took me back to the blog. This picture actually comes from one post in the blog 4 years ago! Again from the Hichhikers' poster, it says it is "the most common New England intertidal barnacle." From Website Lloyd Center for Environment Studies, I know that barnacles are hermaphrodites, which means they are both males and females in their bodies.


I also found many tiny crabs in the tidal pool. It is about 0.9 inch wide without legs. Its back is dark green, they walk sideways. There are thick strips on the legs with spots. The body of the crab is square shape. I think these little guys are Asian shore crabs (Hemigrapsus sanguineus). They have "bended legs, red sports on claws." It has different colors as I saw at the same tidal pool. 



I also saw a green worm when my classmate flipped over. It is similar to sea worms with smaller size. It is really greenish and crawled on the rock. I think it is Green Paddle Worm ( Eulalia viridis).  It can crawl over the rocks as I saw on the shore, and it also can swim. It is about 4 inches. long.

 



http://snails2whales.blogspot.com/2010/08/lovells-island_17.html



Friday, July 25, 2014

Assignment 2

The snails we saw...
I believe they were garden snails. I do not believe that the shell colorings made them different types.
My hypothesis is that birds brought the snails to the rock to make it possible for them to break them open and eat them.
http://eol.org/pages/449908/overview

Lovell island and fishing

The day started with a trip to Lovells Island but stop mid way to take advantage of the good fishing spot. Our quarry was a massive striper, two flounder, and x.

After fishing we went to the island and studies the shoreline where we found tide pools with beautiful rocks, small crabs, and a lot of barnacle. Remnants of old military installations dotted the island but nature over came it.

Afterwards we found evidence of land snails on a rock that led me to believe birds smashed them. I also think that other campers might have brought adventurous snails with them in their gear.

Assignment Part 2

In Lovell's island we found some interesting shells on the rocks of an old WWII era bunker. The shells were of white lip garden snails that somehow made their way onto the island.
The weirder thing about these snails is that they were not alive, they had been cracked open by something and left empty shells on the rocks of the beach. 

With some research it became clear that birds pick up the snails to eat and fly them over rocks, they then drops the snails to crack the shells and get to the soft tissue to eat. 


While the snails do come out a night, we were able to find some alive in the day.

Assignment Part 1

On Friday July 18 we took boat captained by the amazing Captain Charlie, out for a fishing trip in Boston Harbor. After some rocky waves we finally settled at a good spot and patiently waited for our worm baited lines to catch something.

First came the Silver Hake, a very elegant fish that is also called a whiting. While I am not the best at drawing I think I did a good job on drawing this fish as you can see in my notes below ..especially on those clear fins on the underside of the fish.
 These little guys were about 8 inches long but with a whole lot of fight in them.


Next came the Black Sea Bass also called Centropristis Striata by scientist. This fish is a very tough and foot long looking guy, camouflaged perfectly for the rocky bottoms of the ocean floor.

The flounder came next, with 16 inches of amazing evolution and having its eyes on the left. While I could not find the specific named I found that these guys are in the family of Bothidae which are left eyed species that lay on their right side on the ocean floor.



For the main piece in our great fishing expedition we caught a 38inch Striped Bass(Morone Saxatilis) that weighted about 50 to 60 pounds! This fish was amazing in size and flavor as well since we got to take home some of it. 
 Fun Fact: these guys breed in fresh water, then migrate to salt water.



Having ended in with a great big fish, we headed out to Lovell's island were we saw many great little sea critters in the tide pools.

We encountered a great army of common periwinkles all over the beach, they had invaded and held the beaches long before we arrived. 
 To reinforce this invasion the armored Asian Shore Crabs were on the beach as well. This invasive species are extremely effective at clearing the beaches of local sea life.. effectively clearing the path for the waves of common periwinkles to come. 

 We also saw many many outposts of Barnacles surveying the beaches for the sea invasion. On the rocks there were thousands upon thousands of them, their capability to survive outside the water made them ideal for their role in taking over the beaches and holding them along with the Common periwinkles.

Lastly some sneaky hermit crabs disguised as periwinkles were found crawling along the beaches, a very effective covert infiltration into the ranks of the invading periwinkle army.




Fishing and Lovell Island

So first of all, yes, I did hook the biggest fish of the day. That was me. Please, no applause - I'm much too humble for that. Of course, I didn't reel it in mind you; I have people for that.

Now for notes. I think they were better than my last batch, but could definitely use some work. I re-wrote some of them to organize them better (and because my little notebook got crushed in my bag), so hopefully they're readable.

This page describes our first task - which was to take the boat to the deepest and coolest waters in the harbor (the main shipping channel) and fish! Bruce mentioned that the water is cooler now than it was last year at this time, and that that would likely affect which species we encounter and what we'll find in their stomachs.

I attempted a few drawings of the sea worms we were using for bait as well.


Next I've got some notes on the fish we caught. The first was a black bass that was about 14". I noted that it had 4 fins behind it's head, two on the bottom and one on each side. It had a dorsal fin running from about 1/3 it's length back from it's head down to where the tail narrowed. It had a fin on the bottom just below where the tail narrowed (which i now know is an 'anal' fin), and then it's tail fin.

The first one we caught had a noticeable bump on the top and just behind it's head, which Bruce pointed out as a sign that it was in the process of changing from a female to a male. The eyes looked about 1/3" to me and it had two very small rows of teeth. It's scales were iridescent purple and blue in some areas and overall it had a black and white pattern.


 Here's a photo of the black bass:


 We caught 2 flounders as well one about 12" and the other 16". They were both right-sided meaning their bellies were positioned to the right









Here are my drawings of the bass and flounder:






When we got to the tide pools at Lovell island, the tide was still fairly low but was making it's way back in. I found my Asian shore crab, periwinkle, and some barnacles, and also picked up some slipper shells. Here are my notes and drawings of the slipper shells:




The periwinkle:


Two types of barnacle, that I believe are little greys (the small ones) and a northern rock (the larger one with ridges.





And finally here is my Asian shore crab:





And one more picture: this is Charlie, our boat captain cleaning the big striper we caught. when he cut open the belly there was nothing in there - I assume because the unusually cold water is affecting the population of whatever he would normally eat.