Name: Alternative Method of Removing Otoliths from Sturgeon (Video) | JoVE Journal
Uploaded: 2016-06-27T15:00:00.000+00:00
Duration: 5 min 7 s
Description: Learn an alternative method for extracting undamaged otoliths from threatened Lake Sturgeon. This technique preserves ear bone integrity while enabling age and growth studies in rare fish populations.

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5 minutes

Special thanks to the St. Regis Mohawk Environmental Division, Welaka National Fish Hatchery, US Fish and Wildlife Service Research Unit, Southern Illinois University, US Fish and Wildlife Service Northeast Fisheries Center, Sterling Caviar, University of California-Davis, Garrison Dam National Fish Hatchery, Bears Bluff National Fish Hatchery, and US Fish and Wildlife Service Panama City Fisheries Resource Office for their help supplying sturgeon for this project.&#160;This article is Contribution 2013 of the USGS Great Lakes Science Center.

Important Note: Due to the protected status of all species of sturgeon in the United States, permits to acquire and handle fish were obtained prior to laboratory procedure. All specimens were acquired from hatchery sources post mortem due to natural causes and disposed of following standard procedure.
1. Specimen Preparation
<ol>
	<li>Before any incisions lay sturgeon carcass on its side and using a measuring tape to measure total length from the snout to the tip of the tail to the nearest 1 mm. (Figure 1A)</li>
	<li>Weigh sturgeon carcass on a tared scale to the nearest 1 g. Evaluate carcass for any external tags or marks and record.</li>
</ol>
2. Otolith Extraction
<ol>
	<li>Make a vertical incision with a large fillet knife between the base of the skull and the first dorsal scute through the body to separate the head from the body (Figure 1B). After removing the head, turn the head so the mouth is facing up (Figure 1C).</li>
	<li>Remove soft tissue of the mouth and gills by using the fillet knife to cut along the ventral side of the skull (Figure 1D). Make an incision with an electric bone saw from the tip of the snout to the base of the skull to completely bisect the head (Figure 1E). Separate the two halves by hand to expose the brain cavity (Figure 2A).</li>
	<li>Remove and discard brain matter (Red box left) with forceps to view semicircular canals (Red box right) within the brain cavity (Figure 2B).</li>
	<li>Remove semicircular canal cartilage from brain cavity with forceps (Figure 2C). Carefully puncture semicircular canal cartilage with the tip of the forceps and remove otolith (Figure 2D). Remove the otolith (hard bony structure inside the cartilage) with forceps from the semicircular canal cartilage (Figure 2E).</li>
	<li>Repeat steps 2.3 - 2.4 to remove otolith from the other half of the skull.</li>
	<li>Dip the otoliths in 92% Ethanol for 5 sec to remove any cartilage. Place otoliths in an open 25 ml scintillation vial to dry for 24 hr.</li>
</ol>

<ol><li>Auer, N. A. Conservation. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aAuer%2C+NA+%22Sturgeons+and+Paddlefish+of+North+America%22">Sturgeons and Paddlefish of North America</a>. LeBreton, G. T. O., Beamish, F. W. H., McKinley, R. S. 27, Kluwer Academic Publishers. 252-276 (2004).</li>
<li>Sturgeon Specialists Group, sturgeon conservation. IUCN (International Union for the Conservation of Nature). , Source: 
 <a target="_blank" href="www.iucn.org">www.iucn.org</a> (2008).</li>
<li>Campana, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Accuracy%2C+precision+and+quality+control+in+age+determination%2C+including+a+review+of+the+use+and+abuse+of+age+validation+methods%29%5BTitle%5D)+AND+%22Journal+of+Fish+Biology%22%5BJournal%5D)">Accuracy, precision and quality control in age determination, including a review of the use and abuse of age validation methods).</a> Journal of Fish Biology. 59, 197-242 (2001).</li>
<li>Bruch, R. M., Campana, S. E., Davis-Foust, S. L., Hansen, M. J., Janssen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Lake+Sturgeon+age+validation+using+bomb+radiocarbon+and+known-age+fish%5BTitle%5D)+AND+%22Transactions+of+the+American+Fisheries+Society%22%5BJournal%5D)">Lake Sturgeon age validation using bomb radiocarbon and known-age fish.</a> Transactions of the American Fisheries Society. 138, 361-372 (2009).</li>
<li>Baremore, I. E., Rosati, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+validated%2C+minimally+deleterious+method+for+ageing+sturgeon%5BTitle%5D)+AND+%22Fishery+Bulletin%22%5BJournal%5D)">A validated, minimally deleterious method for ageing sturgeon.</a> Fishery Bulletin. 112, 274-282 (2014).</li>
<li>Stevensen, J. T., Secor, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Age+determination+and+growth+of+Hudson+River+Atlantic+sturgeon%2C+Acipenser+oxyrhynchus%5BTitle%5D)+AND+%22Fishery+Bulletin%22%5BJournal%5D)">Age determination and growth of Hudson River Atlantic sturgeon, Acipenser oxyrhynchus.</a> Fishery Bulletin. 97, 153-166 (1999).</li>
<li>Brennan, J. S., Cailliet, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Comparative+age-determination+techniques+for+white+sturgeon+in+California%5BTitle%5D)+AND+%22Transactions+of+the+American+Fishery+Society%22%5BJournal%5D)">Comparative age-determination techniques for white sturgeon in California.</a> Transactions of the American Fishery Society. 118, 296-310 (1989).</li>
<li>Rossiter, A., Noakes, D. L. G., Beamish, F. W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Validation+of+age+estimation+for+the+lake+sturgeon%5BTitle%5D)+AND+%22Transactions+of+the+American+Fisheries+Society%22%5BJournal%5D)">Validation of age estimation for the lake sturgeon.</a> Transactions of the American Fisheries Society. 124, 777-781 (1995).</li>
<li>Chalupnicki, M. A., Dittman, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((North+American+Sturgeon+Otolith+Morphology%5BTitle%5D)+AND+%22Copeia%22%5BJournal%5D)">North American Sturgeon Otolith Morphology.</a> Copeia. , 260-266 (2016).</li>
<li>Secor, D. H., Dean, J. M., Laban, E. H. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aSecor%2C+DH+%22Manual+for+otolith+removal+and+preparation+for+microstructural+examination%22">Manual for otolith removal and preparation for microstructural examination</a>. , Barach Press. Columbia, South Carolina. (1991).</li>
</ol>

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The overview of an alternative method of extracting otoliths from sturgeon carcasses has been detailed. It is important to note that special attention is needed to the lateral incision placement on the midline of skull in order to bisect the skull evenly to ensure no harm to the otoliths during dissection. If the incision is not deep enough to completely bisect the skull it will be very difficult to expose the brain cavity where the location of the otoliths is clearly visible. With experience, the overall technique is re...

Sturgeon (Acipenseridae) populations throughout the world have been declining for over a century due to impacts including habitat loss, population fragmentation, and overfishing such that many populations are protected by state and federal laws1,2. Management agencies throughout the USA and the world have identified sturgeon as a target species for restoration and recovery1. Population characteristics (growth, recruitment, diet) of most sturgeon populations have been studied to better understand basic biology and life history characteristics1. Due to the protected status of most sturgeon populations, age evaluation is difficult in small threatened populations where no sacrifice or harm to individuals is warranted.
The extraction of bony structures for the purpose of age estimation and growth analysis has been a common technique3.The use of fin ray sections to determine age of sturgeon has become a practical nonlethal method, but verification of the technique has been limited and age can be very difficult to decipher in older individuals (&#62; 15 years)4. Researchers evaluating the use of multiple bony structures in sturgeon for their use in validating the age of Gulf Sturgeon (Acipenser oxyrinchus desoti)5, Atlantic Sturgeon (A. o. oxyrinchus)6, White Sturgeon (A. transmontanus)7, and Lake Sturgeon (A. fluvescens)8 concluded that the first marginal pectoral fin ray provided the most accurate age but concluded this invasive procedure to be deleterious to larger individuals. &#160;Currently, there is the development of using otolith shape metrics to distinguish between North American sturgeon species with a very high rate of success9. Details on the process of removing the otolith with a dorsal transverse incision at the base of the skull is a common otolith extraction method found throughout the literature and clearly detailed by Secor et al. (1991)10. However, this method is difficult to implement on sturgeon that have very thick skulls with otoliths that are small and delicate and would tend to break. A further review of the literature shows no other detailed methodology of the otolith removal process for sturgeon. The objective of this paper was to detail an alternative method of extracting otoliths from sturgeon by entering the brain cavity from the ventral side.

<table><tbody><tr><td>Measuring Board</td><td></td><td></td><td>Metric meter stick is preferred</td></tr><tr><td>Weighing scale</td><td></td><td></td><td></td></tr><tr><td>Filleting Knife</td><td></td><td></td><td></td></tr><tr><td>Scalpel</td><td></td><td></td><td></td></tr><tr><td>Forceps</td><td></td><td></td><td></td></tr><tr><td>Sample vials</td><td></td><td></td><td>25 ml scintillation vials work well</td></tr></tbody></table>

alternative method of removing otoliths from sturgeon

Alternative Method of Removing Otoliths from Sturgeon

Extracting the otoliths (ear bones) from fish that have very thick skulls can be difficult and very time consuming. The common practice of making a transverse vertical incision on the top of the skull with a hand or electrical saw may damage the otolith if not performed correctly. Sturgeons (Acipenseridae) are one family in particular that have a very large and thick skull. A new laboratory method entering the brain cavity from the ventral side of the fish to expose the otoliths was easier than other otolith extraction methods found in the literature. Methods reviewed in the literature are designed for the field and are more efficient at processing large quantities of fish quickly. However, this new technique was designed to be more suited for a laboratory setting when time is not pressing and successful extraction from each specimen is critical. The success of finding and removing otoliths using this technique is very high and does not compromise the structure in any manner. This alternative technique is applicable to other similar fish species for extracting the otoliths.

The adult size of sturgeon across the world varies greatly but the location of the otoliths is consistent. The use of a sharp fillet knife was found to remove the soft tissue of the mouth easily shown in Figure 1D. An electric bone saw is the preferred tool for the lateral incision to expose the brain cavity in Figure 1E. However, attention to bisecting the midline of the skull is needed otherwise the otoliths may be crushed during this process. If this p...

The goal of the protocol is to show an effective method to extract the otoliths from sturgeon carcasses.

Extracting the otoliths (ear bones) from fish that have very thick skulls can be difficult and very time consuming. The common practice of making a ...

The overall goal of this method is to provide an effective alternative technique for extracting undamaged otoliths from threatened fish, such as Lake Sturgeon. This otolith extraction method can help answer key questions about fish age and growth, the placement of ear bones in relation to the brain morphology, and habitat correlated microchemistry. The advantage of this technique is that in fish with thick skulls and fragile otoliths, opening the brain cavity doesn't harm the otoliths or disrupt other critical structures.The idea for this method was developed during research on the restoration ecology of threatened Sturgeon. In remnant populations, specimens for necropsy and laboratory analysis are rarely obtained. So successfully collecting age and other information from individual animals is critical for filling species'data gaps.Mark will be preforming the procedure of removing the otoliths from the Lake Sturgeon. To extract the otoliths, first lay the Sturgeon on its belly and use a measuring tape to determine the total length from the snout to the tip of the tail to the nearest one millimeter. Next, weigh the animal on a tared scale to the nearest one gram and evaluate the body for any external tags or marks.After recording these data, use a large fillet knife to make a vertical incision through the body between the base of the skull and the first dorsal scute to separate the head. After its removal, turn the head so the mouth is facing up. Then use the fillet knife to cut along the ventral side of the skull to remove the soft tissue.Followed by an electric cast cutter incision from the tip of the snout to the base of the skull to completely bisect the head. Separate the two halves by hand to expose the brain cavity. Then use forceps to remove and discard the brain matter to expose the semi-circular canals within the brain cavity.Remove the semi-circular canal cartilage from the brain cavity. Then use the tip of the forceps to carefully puncture the semi-circular canal cartilage. After identifying the hard bony structure within the cartilate, withdraw the otolith and dip the ear bone into 92%ethanol for four seconds to remove any remaining cartilage.Finally, dry the otolith in an open 25 milliliter scintillation vial for 24 hours. The adult size of Sturgeon across the world varies greatly, but the location of the otoliths is consistent. As demonstrated, a sharp fillet knife easily removes the soft tissue of the mouth.An electric cast cutter is the preferred tool for the lateral incision to expose the brain cavity however. Careful attention to the bisection of the mid-line of the skull is needed. Otherwise, the otoliths may be crushed during the process.Forceps facilitate the straightforward removal of the brain matter, allowing access to the semi-circular canal cartilage which contains the otolith at the base of the brain cavity. The cartilage in the semi-circular canal can then be removed from the otolith with little trouble using forceps for further ear bone analysis. Once mastered, this technique can be completed in less than five minutes if it is performed properly.While attempting this procedure, it's important to remember to take your time making the incisions. Don't forget that working with dissecting instruments and dead fish can be dangerous and smelly. So precautions such as proper use of the surgical instruments and suitable PPE should always be taken while performing this procedure.After watching this video, you should have a good understanding of how to open the skull of the Sturgeon from the ventral side and remove the otoliths with no damage to the ear bones. After its development, this technique paved the way for researchers in the field of fisheries science to explore alternative ways to successfully remove otoliths in fish species where standard techniques proved difficult.

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Learn an alternative method for extracting undamaged otoliths from threatened Lake Sturgeon. This technique preserves ear bone integrity while enabling age and growth studies in rare fish populations.

Alternative Method of Removing Otoliths from Sturgeon

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