Aging Giant Pacific Octopus using Beaks and Stylets for Better Stock Structure Assessment Ashley , Dr. Scarlett Oregon State University, Marine Team
Introduction Results Discussion Despite being a highly charismatic and frequently exhibited organism, Out of all the specimens collected, 30 had 2-5 cross sections taken which resulted in 78 embedded stylets. Originally, 24 stylets were determined Giant Pacific Octopus (Enteroctopus dofleini) population dynamics to be useable for counting growth rings. Through the process of sanding and polishing followed by analysis with a microscope, that number was The main purpose of this project was to create an efficient and are poorly understood. Basic monitoring data for this species is reduced to 15. Growth rings were visible on both beaks and stylets, as seen in figures 2 and 3 respectively, meaning that both hard parts could accurate method for aging the Giant Pacific Octopus. This project shed some much needed light on the population age structure of this limited to bycatch and stomach contents of other fisheries species. An potentially be used to obtain actual age estimates. This also implies that the methods used for embedding could be repeated in the future. A essential step to a better estimation of population size and species, which will help people better understand the ramifications counting protocol was written to standardize how the age estimates would be obtained by different counters. Figure 4 shows that the stylet wet productivity is to establish efficient procedures and accuracy of a size of bycatch or directed fisheries. By defining weight as a proxy for weight had a positive correlation with the total body weight and an R value of 0.7583. at age model. The objectives of this research project are to determine age, this research can also provide an alternate, non-lethal method the most efficient method for analysing the hard parts of the Giant for estimating age. This information has the potential to assist in Pacific Octopus (GPO) (Figure 1), and to provide fisheries planning conservation strategies and management of related management professionals with a weight at age relationship for fisheries. population stock structure modelling. This information would be All of the beaks and stylets experienced a significant amount of extremely useful in reducing bycatch that can cause serious economic stress through the dehydration process both when they were initially issues through fishery closures. extracted and before being embedded. This is most likely, the reason why the number of usable stylets was so low compared to the total number of specimen collected. Future GPO aging studies should take special action to avoid this. This work represents one of the very first attempts at finding methods to age GPOs. The fact that growth rings were seen in both the beaks and stylets indicates that both hard parts have the potential to be used to attain actual age estimates in future studies. Broader Impacts Having an accurate size at age model would be extremely valuable to those trying to create a population stock structure model for GPOs. Figure 1. Left: GPO beak Right: GPO stylet This would aid any conservation efforts for the species and direct fishing regulations. Methods References Embedding process Barratt, Iain M., and A. Louise Allcock. "Ageing octopods from stylets: development of a technique for permanent preparations." ICES Journal of Marine Science: Journal du Conseil 67.7 (2010): 1452-1457. • 2-3 cross sections were cut from 1 stylet of each specimen and Photo: Monterrey Bay Aquarium Figure 2. Top: Composite image of GPO beak. Bottom: Zoomed in image of area inside box to show growth rings. embedded Conners, M. Elizabeth, and Christina L. Conrath. "22. Assessment of the Octopus Stock Complex in the Gulf of • They were dehydrated from 70% to 100% ethanol Alaska." (2011). • Each cross section was embedded using LR White Hermosilla, Consuelo A., et al. "Age validation in common octopus Octopus vulgaris using stylet increment • Cross sections were sanded with 800-2000 grit paper and analysis." ICES Journal of Marine Science: Journal du Conseil (2010): fsq054. polished with 5.0 and 1.0 alumina solution Hernández-López, José L., José J. Castro-Hernández, and Vicente Hernandez-Garcia. "Age determined from the daily deposition of concentric rings on common octopus (Octopus vulgaris) beaks." Fishery Bulletin-National Imaging for stylets Oceanic and Atmospheric Administration 99.4 (2001): 679-684.
• Compound microscope and AmScope software were used to Leporati, Stephen C., and Anthony M. Hart. "Stylet weight as a proxy for age in a merobenthic octopus analyse the stylets and take images population." Fisheries Research 161 (2015): 235-243.
• Images from the core to the outermost edge of the stylet were Leporati, S., Jayson M. Semmens, and Gretta T. Pecl. "Determining the age and growth of wild octopus using taken and strung together so that a count could be taken stylet increment analysis." Marine Ecology Progress Series 367 (2008): 213-222. • Secondary counts were conducted by another person to Perales-Raya, Catalina, et al. "Age estimation obtained from analysis of octopus (Octopus vulgaris Cuvier, 1797) improve accuracy. Any stylet that had a difference of more than beaks: improvements and comparisons." Fisheries Research 106.2 (2010): 171-176. 3 rings between the two counts was discarded Perales-Raya, Catalina, et al. "Age validation in Octopus vulgaris beaks across the full ontogenetic range: beaks as Figure 3: Top: Zoomed out image of an embedded cross section of a stylet. recorders of life events in octopuses." Journal of Shellfish Research 33.2 (2014): 481-493. Imaging for Beaks Bottom: Zoomed in image of the area inside the box showing growth rings. Acknowledgements: • Beaks were cut in half Liz Conners – NOAA, National Marine Fisheries Service, Alaska Division • Dissecting microscope was used to look for growth rings on Heppell lab – Oregon State University the inner lateral wall Ryder Hom – Oregon State University Figure 4: Plot of total body weight and average stylet weight for all Giant Pacific Octopus individuals collected. Miranda Toner – Oregon State University