Why are some clutches abnormal?

Veronika Brzeski Latest News, Science & Conservation

Guest post by Feng Tang, graduate student with the NSERC Canadian Fisheries Research Network

Feng Tang 0624Definition: A clutch is a batch or a brood of eggs.

At sea sampling since 2011 has brought attention to berried females carrying abnormal clutches — where less than 50% of the tail is covered with eggs. As maintaining or improving egg production is a key component to maintain the lobster fishery’s sustainability, it is important to determine what factors are causing the abnormal clutches.

Last year, we selected 10 sites across eastern Canada (5 with consistently high incidence of abnormal clutches and 5 with low incidence). We collected mature pre-spawn females (that were going to lay their eggs during last summer) from these sites, and counted the eggs inside their body.  We tested if the abnormal clutches were caused by females not having enough energy to produce full clutches. We found that this is not the case.

Instead, we found that all of the abnormal clutches found in the lab were carried by the females that had a very low amount of sperm stored in their body. Our hypothesis is that the abnormal clutches found in the field might caused by the low amount of sperm received by the females. However, this finding was only based on a small scale lab study, and we wanted to verify this finding in the field by comparing the leftover amount of sperm in the female’s sperm storage chamber between berried females that are carrying abnormal clutches and those of the same size carrying normal clutches.

We  selected 2 sites to collect our berried females from. One is in the Bay of Fundy and the other one is in LFA27. After the lobsters are brought into our lab, we will compare 1) their body condition, 2) number of internal eggs that are going to be spawned next year, 3) number and size of external eggs, and 4) leftover  (residual) amount of sperm in their sperm storage chamber.

Stay tuned for our results!

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