Hatching periodicity, survival and development of the early life stages of red deepsea crab (chaceon quinquedens) in laboratory conditions: effects of diet and temperature
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A decline in commercial crustacean species (lobsters, king crab, etc.) has caused an increased interest in the harvest of the red deepsea crab Chaceon quinquedens. The red deepsea crab fishery is federally managed by the New England Fishery Management Council-Deep Sea Red Crab Fishery Management Plan (FMP), but little is known about this species’ general biology, especially conditions required for larval survival. This multiyear project aimed to answer two main questions about the life history of the red deepsea crab. First, is there a common larval hatching pattern between adult female crabs? Specifically, what is the duration of the hatching process, at what time of the day do larvae hatch, and what is the relationship between female morphometry and the total larvae hatched? Second, what are the factors affecting the survival and development of larval red deepsea crab? In order to answer these research questions, I studied the effects of diet (rotifers, Artemia sp., algae, and unfed), temperature (9, 15, and 20°C), and aquaculture systems.
Ovigerous females were obtained from commercial traps and transported to the NOAA James J. Howard Laboratory, Sandy Hook, NJ. They were placed in the Females Husbandry and Hatching Collection System (FHCS) where the larvae hatched. Hatching of adult females was monitored and measured by volume. A group of them was observed for 3 consecutive days in 4 hours intervals. First stage zoeae were obtained from eggs that hatched in FHCS. The 2014 flow-through system consisted of two temperature tanks (9 and 15°C) containing 10 buckets each. Inside each bucket, three cylindrical containers with capacity for 10 larvae each. That year diets included unfed, rotifers, and algae treatments for each temperature. The 2016 recirculating system had two temperature tanks (15 and 20°C), each containing 12 conical upwellers with capacity for 20 larvae each. Diets for 2016 included unfed, rotifers, Artemia sp. and a mixture of the last two, for each temperature. Larvae were fed and counted daily.
A simple linear regression (SLR) was calculated to predict the number of larvae hatched based on the measured volumes. This SLR was significant (F = 1196; df = 1, 13; R2 = 0.9892, P = 3.498e-14) for the relationship. The mean duration of hatching period for red deepsea crab females is 18.1 ± 3.5 days, with a daily lower mean number of larvae hatched at 14:00 hr (mid-day from10 am to 2 pm) than at time 22:00 hr (6 pm to 10 pm) across all crabs, but not different from the other time intervals.
Daily recorded larvae mortality data was analyzed for survival and development hypotheses using non-linear mixed effects models (NLME). In 2014, the model was highly significant, temperature and its interaction with the rotifers diet are different from the other treatments mortality, supporting a longer survival on larvae under these treatments. The fewer larvae that survived longer were also in advanced larval development stages (Zoeae III and IV). During 2016 survival temperature was also the main factor affecting larvae mortality. Temperature, diet, and their interaction affected the capacity of the RDSC larvae to reach advanced stages of development in the years of experiments.
Comparison of both years Larvae Feeding Experimental System (LFS) showed that the type of aquaculture system plays an important role in the mortality of the RDSC larvae with longer survival recorded using the 2014 LFS I. In addition, one of the expected outcomes of these experiments was to answer which feed was the best among rotifers, Artemia sp., and algae for the RDSC larvae in laboratory conditions. I found rotifer and Artemia sp. as the best live food option for the RDSC larvae.
My research findings on the optimal survival conditions of the species will facilitate further research in marine aquaculture, to better understand the ecology, fishery, and impacts of climate change on the life history and fishery of red deepsea crab.