Crabbing Research-Success!

Hello!

 

After many trials and error, I finally had some success with gathering my crab samples. Took a little longer than expected though. I guess I’ll start off by talking about my second attempt, and then onto the final, successful third attempt.

 

So for the second attempt, I felt much more confident since we had the proper nets. In total we had 3 nets, two of them being the small circular ones, and the other being the big unsuccessful one. I began by placing the bait in all the traps, then setting my 15 minute timer, and then throwing the net into the water. Immediately after, we noticed the seal coming our way. I didn’t give it to much thought since the seal wasn’t a problem the previous time, but this time...it was. The 15 min was up and I began pulling the nets up. When one of the small nets came up, a small red rock crab was in the net, but the bait and the bag holding the bait was completely gone. When we pulled up the other two traps, same thing. All our bait, and our methods for keeping the bait on the traps were gone. I must admit I got quite frustrated at the seal, I used to like seals, not so much any more. Even though this attempt was even more of a failure than the first, it prepared us for the next attempt, which was a success.

Moving on.

 

We had learned our lesson from having everything ruined by the seal, and this time we came prepared. Apparently, directly zip tying your bait to the trap, makes it hard for the seals to get, but easy for the crabs to see and find. So we tried. Once again we set up all our equipment, cast the nets and waited. We caught some crabs here and there, but once in a while there would be 4 crabs in one net. It was quite hard to gather all my data when you have a bunch of crabs trying to get away while you doing it. As you will see from the data sheet, there was a lot of things I was trying to measure and record.  

Crab Data Collection sheet:

 

Date: May 3rd 2018

Bait used: chicken neck/ back

Weather:  Sunny/Calm water/little wind

Location: Belcarra docks

Ocean bottom landscape: Rocky/ sandy with vegetation

Time interval: 15 minutes

Water temperature: unknown

 

Crab Number

Time of catch

Tidal period

Crab weight

Crab size

Crab sex

Crab type

Net type

1.

6:15pm

2.33m up

200g

11cm

F

R

S

2.

6:15pm

2.33m up

250g

12.5cm

F

D

S

3.

6:15pm

2.33m up

200g

11.5cm

F

R

S

4.

6:15pm

2.33m up

225g

12.5cm

F

D

S

5.

6:25pm

2.44m up

225g

11.75cm

F

D

B

6.

6:25pm

2.44m up

250g

13.7cm

M

R

B

7.

6:25pm

2.44m up

100g

10.3cm

M

R

B

8.

6:30pm

2.52m up

325g

14.4cm

F

D

S

9.

6:45pm

2.66m up

200g

11.7cm

F

D

S

10.

       

11.

       

12.

       

13.

       

14.

       

15.

       

 

Before continuing, the data sheet above has only the data collected on that particular date, I will be talking about all my data collectively which includes 3 more crabs than that on the list above.

I’ve talked about the experience, and how I got the data, but let's talk about the actual data. The first thing I noticed was the male to female ratio. When taking all 12 crabs into consideration, 33 percent were male and the rest were female. This was to be expected do to the laws, but I was still surprised by how little males there were.

When looking at crab types, there seemed to be a balance of almost 50/50 of red rock VS dungeness.  

As you can see, most of the crabs were caught on the small nets(S), this was also to be expected. One thing though that was more of an observation rather than hard data, is that almost none of the people on the dock were catching crabs large enough to keep. We were closely monitoring other people catch(roughly around 10 people crabbing at the dock with multiple nets) and only one person caught crabs large enough to keep. Same was with our data, none of the crabs were of legal limit.

 

Moving onto the weights of the crabs, they were all quite similar except for one outlier. Most ranging between 100-300 grams. Of course there weight was directly related to there size as well. The heavier the crab, the bigger the shell.

 

I thought before ending this I would remind everyone reading what I plan to do with this data, for those of you who don’t know. This was the first part of the data sampling, the next one will occur in a much different location with extremely little fishing occuring. This way I’ll be able to do a comparison between what I found at the Belcarra docks, which is a very popular crabbing location, and another location.

 

Thanks for reading, stay tuned for more!

  




Attachments

Photos (5)
Original Post

Hey Kian!

What are fabulous post. The photos helped explained what you were talking about for sure and it was really cool to see your research has led to a success! 

Slightly funny, that a seal was a variable you had to count in but hey, this is nature we are experimenting with so there is bound to be animals out there that can affect the results in some way or form. 

A suggestion is that while it is somewhat inaccurate, I noticed the water temperature was unknown. Perhaps different weathers may affect the results as well. Anyway, 

Maybe a basic thermometer and plug that into the water and leave it for a good solid 5-10 minutes can probably give you some reading on what the temperature is!

 Image result for thermometer

Cool things, keep it up! 
~Jim
CA
CBSS 

Hey Kian!

Great post! It was easy to understand (especially with the pictures) for us folk that aren't super educated on the whole crab front. All of your information was clearly laid out and easy to follow. 

I wonder why the male to female ratio was dramatically different, maybe that's something you can look into in the future. And perhaps the crabs are just genetically getting smaller?

Can't wait to see what's to come!

Hey Kian,

This was a really cool post. Your observations and processes were well-explained and were easy to understand, which was great. Also, your research is intriguing because not only did you have some research, but most of it was done in the field. Following up with what Alanna said about the crabs genetically getting smaller, could this be a result of too many people catching the ones with bigger shells and the ones left over are the ones which pass on their smaller-shelled traits, increasing that allele frequency? Or is it generally common within the area for red rock crabs and dungeness crabs to be smaller?

Again, great work!

Maiya

Add Reply

×
×
×
×