World Aquaculture 2023

May 29 - June 1, 2023

Darwin, Northern Territory, Australia

A NOVEL LOW-COST SPECTRAL SYSTEM TO SENSE APPROACHING ECDYSIS IN CULTURED JUVENILE TROPICAL ROCK LOBSTER Panulirus ornatus

Charles Sutherland*, Alan Henderson, Dean Giosio, Andrew Trotter, Gregory Smith.

 School of Engineering,

             University of Tasmania, Dobsons Rd,

             Sandy Bay, TAS, 7005, Australia.

             charles.sutherland@utas.edu.au

 



Detecting approaching ecdysis of juvenile tropical rock lobsters (Panulirus ornatus) is a pathway to reduce conspecific cannibalistic interactions in culture. A spectral signature created by nutrient and mineral reabsorption from the integument is a possible pre-ecdysis detection solution. Sensitive electronics in a salt-water environment coupled with the expense of a scientific grade spectrometer has promoted investigating lower-cost possibilities. A low-cost spectral system was constructed for testing and comprised of a Sony IMX-219 NOIR based camera, an AMS AS7269x 18 channel (6 near infrared channels) sensor array, and Osram SFH-4737 broadband infrared LEDs. The system was coordinated for simultaneous data collection through a Nvidia Jetson Nano with all components costing less than AUD $500. The system coordinates near simultaneous (<100 ms) collection of image and spectral data, adding an augmented layer of spectral data to the image. Lobsters near ecdysis (with developed suture lines), intermoult lobsters and post-ecdysis lobsters (following morning) were compared. We showed that IR reflectance and green channel pixel percentage are two separate effects because they did not correlate in the sample groups (Pearson’s Correlation, Intermoult P>0.74, Pre-ecdysis P>0.54, Post-ecdysis P>0.81). Even so, the low-cost, low sensitivity and low-resolution components of this system were unable to detect a change on the dorsal surface indicating approaching ecdysis. However, the post-ecdysis group had significantly (P<0.01) lower infrared reflectance and significantly (P<0.01) reduced green channel pixel activation than the combined intermoult and pre-ecdysis groups. A scatterplot of the two effects shows that the post-ecdysis lobsters group together and have little overlap with the intermoult and pre-ecdysis groups. This is a promising first step in developing a low-cost spectral solution for detecting pre-ecdysis in juvenile tropical rock lobsters