Shad Identification

This article was written in March 2015, but not published until June.

American Shad - Alosa sapidissima
American Shad – Alosa sapidissima

In North Carolina, members of the family Clupeidae include the herrings, shad, and menhaden. Although members of this family can be found year round, we wanted to specifically mention them today due to the annual spring spawning runs that a few of these species make. Starting in about February, and running through May, the sexually mature (and normally marine) Hickory Shad, American Shad, Blueback Herring, and Alewife Herring will enter area rivers and swim up them to reach their spawning grounds. It is during this time that anglers will commonly encounter them, and with any luck, catch them.

Identification of the various Clupeiform fishes becomes vitally important during their spawning runs, as different rules apply to different species, in different waterbodies. Currently in North Carolina, on the Neuse River, you can keep 10 shad (American or Hickory) in combination, including no more than 1 American shad. For more information, see:

http://www.ncwildlife.org/Portals/0/Regs/Documents/2014-15/Fishing_Regulations.pdf

The aim of this post is to help in identifying the American Shad from the Hickory Shad, as these are the two that we receive the most questions about, and the two most commonly caught on hook and line. If you wish to learn about the other river herrings, please see this pamphlet by the NCWRC:

http://216.27.39.103/Portals/0/Fishing/documents/Herring_Shad_ID_guide_sm.pdf

 

Hickory shad - Alosa mediocris - Top American Shad - Alosa sapidissima - Bottom
Hickory shad – Alosa mediocris – Top
American Shad – Alosa sapidissima – Bottom

American Shad Identification:

American Shad - Alosa sapidissima
American Shad – Alosa sapidissima

The American Shad, Alosa sapidissima, is the largest of all the herrings. Commonly reaching sizes of 50 cm SL (19.6 inches, Standard Length). Like all shad in this article, they have a silvery, metallic sheen, with blues and greens on top, fading to white below. They also have a row of scales on their bellies, known as ventral scutes. These scales are saw-like, very noticeable, and serve as a method to distinguish the river herring  and shads from the sea herrings, which lack these scales. One of the most obvious features to aid in identifying them, is the lower jaw. The lower jaw of the American Shad does not protrude beyond the upper jaw when fully closed. This will become a lot more obvious in the following sections. The American Shad has 59-73 gill rakers on the lower limb of the first gill arch.

Ventral scutes of a Hickory Shad ventral scutes
Ventral Scutes

 

Hickory Shad Identification:

Hickory Shad - Alosa mediocris
Hickory Shad – Alosa mediocris

Hickory Shad are noticeably smaller on average than the American Shad. Commonly to 40 cm SL (15.7 Inches Standard Length). Hickory Shad also have ventral scutes as in the above photograph. The lower jaw of the Hickory Shad protrudes beyond the upper jaw when fully closed. The Hickory Shad has approximately 20 gill rakers on the lower limb of the first gill arch.

Closed Jaws up close:

Hickory shad - Alosa mediocris
Hickory shad – Alosa mediocris

Here, in this photo above, you can see the lower jaw of the Hickory Shad protrudes a great deal past the upper jaw when the mouth is closed.

 

American Shad - Alosa sapidissima
American Shad – Alosa sapidissima

Here, in the photo above, you can see the lower jaw of the American Shad does not protrude beyond the upper jaw when the mouth is fully closed. The mouth is in fact open just a bit in this photograph.

Hickory shad - Alosa mediocris - Top American Shad - Alosa sapidissima - Bottom
Hickory shad – Alosa mediocris – Top
American Shad – Alosa sapidissima – Bottom

Some of the other more common Clupeids in our area include the Gizzard Shad, Dorosoma cepedianum, the Atlantic Menhaden, Brevoortia tyrannus, the Atlantic Thread Herring, Opisthonema oglinum, and the Threadfin Shad, Dorosoma petenense.

Atlantic Thread Herring - Opisthonema-oglinum - Top Atlantic Menhaden - Brevoortia-tyrannus - Bottom
Atlantic Thread Herring – Opisthonema-oglinum – Top
Atlantic Menhaden – Brevoortia-tyrannus – Bottom
Dorosoma cepedianum - Gizzard Shad - Top Brevoortia tyrannus - Atlantic Menhaden - Bottom
Dorosoma cepedianum – Gizzard Shad – Top
Brevoortia tyrannus – Atlantic Menhaden – Bottom
Atlantic Thread Herring - Opisthonema oglinum
Atlantic Thread Herring – Opisthonema oglinum

We will be adding additional photographs as we encounter them!

 

Ranges in North Carolina:

Alosa aestivalis Range in NC
Alosa aestivalis Range in NC
Alosa sapidissima Range in NC
Alosa sapidissima Range in NC
Alosa pseudoharengus Range in NC
Alosa pseudoharengus Range in NC
Alosa mediocris Range in NC
Alosa mediocris Range in NC

 

Read More

Vermillion vs Silk Snappers

Lutjanus vivanus vs Rhomboplites aurorubens
Top: Vermillion Snapper – Rhomboplites aurorubens
Bottom: Silk Snapper – Lutjanus vivanus

 

Today we are starting a series of posts that will showcase some of the fishes we encounter on a weekly basis. We plan on including both common fishes, oddballs, a little biology, and lots of pictures! Often we find fishes that are everyday sights to us, may be very interesting to people who don’t have the luxury of seeing them as often. With that in mind, I wanted to start off by covering the differences between two common species of snapper that I saw today, the vermillion snapper (Rhomboplites aurorubens) and the silk snapper (Lutjanus vivanus). As adults these two species are easy to separate, as the silk snapper grows much larger, but between 10 and 20 inches these fishes are often mixed up.

Upon an initial glance, the two species seem awfully similar, they are both red, both snappers, and both have faint parallel yellow lines along their sides. Looking at a still picture of both fishes side by side, one obvious difference is the eye color.

 

Silk Snapper - Lutjanus vivanus - Close up
Silk Snapper – Lutjanus vivanus – Close up of Yellow Lines

 

Vermillion Snapper - Rhomboplites aurorubens - Close up
Vermillion Snapper – Rhomboplites aurorubens – Close up of Yellow Lines

 

Vermillion snapper have a red eye, while the silk snapper have a diagnostic yellow eye. The silk snapper also has yellow tinged pectoral fins, anal fin, dorsal fin, and caudal fin, where the vermillion is red all around. These yellow tinged fins may be subtle in the above picture, but are much more obvious in person. The vermillion snapper is rather slender compared to the silk, with a smaller head and shorter snout.

 

Silk Snapper - Lutjanus vivanus
Silk Snapper – Lutjanus vivanus

 

Vermillion Snapper - Rhomboplites aurorubens
Vermillion Snapper – Rhomboplites aurorubens

 

The vermillion snapper tends to live in more shallow water than the silk, and is often caught on headboats and charters while bottom fishing wrecks and reefs. The silk snapper on the other hand is generally caught in much deeper waters, and is rarely if ever seen on typical headboat trips.

Finally, both species can be distinguished from the fish they are most commonly confused with, the Red Snapper by the lack of pale yellow bands along its sides.

 

Lutjanus campechanus
American Red Snapper – Lutjanus campechanus

 

Silk Snapper - Lutjanus vivanus
Silk Snapper – Lutjanus vivanus

 

Vermilion Snapper - Rhomboplites aurorubens
Vermilion Snapper – Rhomboplites aurorubens

 

This post is intended to be as generic as possible while still helping readers identify their catch. If you need specifics, the following images will better assist you.

Vermillion vs Silk Snappers

 

Silk Snapper - Lutjanus vivanus
Silk Snapper – Lutjanus vivanus

 

Vermillion Snapper - Rhomboplites aurorubens
Vermillion Snapper – Rhomboplites aurorubens

 

And lastly, a few external links:

Silk Snapper

Vermillion Snapper

 

 

Read More

Amberjack Identification

Introduction

Today I wanted to touch on amberjack identification, specifically, how to properly ID them. Amberjack identification is not the easiest task in the fish world, but with a little practice you shouldn’t have any problems. This is a question we see on a regular basis, and one even experienced captains get wrong repeatedly. I was recently approached by some mates from a local charter boat who were asking how to correctly ID these fishes, and I found it difficult to explain without pictures, so this is my attempt. The fishes we will be referring to as “amberjacks” from here on out include: the Greater Amberjack, Seriola dumerili, the Almaco Jack, Seriola rivoliana, the Banded Rudderfish, Seriola zonata, and the Lesser Amberjack, Seriola fasciata. Although there are 9 fishes in the genus Seriola, these four fishes are the only resident amberjacks present along the eastern coast of the US.

Why does amberjack Identification matter?

Amberjack identification may not matter to you at all, however if you are a fisherman, many states have regulations that cover greater amberjack differently from almaco, lesser and banded rudderfish. You better hope you can tell them apart before you put one in your cooler!

The basics

With very few exceptions, most bony fishes respire though organs called gills, and most of these gills share the same general structure presented below.

Amberjack Identification
A Gill Arch. Rakers are the white projections, filaments the red.

Without going into too much detail, the red string-like structures in this image are known as filaments, and the white protrusions are known as gill rakers. The structure as a whole is known as a gill arch, and many gill arches together make up the gills. The number of rakers on the first gill arch is what we are going to use to ultimately help us identify the differences between the amberjacks.

Size

Before you have to start counting gill rakers, let’s cover the obvious external characteristics. First of all, large adult greater amberjack are easy to identify on their size alone. None of the other amberjacks reach as large of a size as the greaters. Although the almaco jack comes close, its body shape is completely different, and is easily differentiated.

Common Name Max reported Size Common Size
Greater Amberjack 190 cm (74.8 Inches) 100 cm (39.4 Inches)
Almaco Jack 160 cm (62.9 Inches) 90 cm (35.4 Inches)
Banded Rudderfish 75 cm (29.5 Inches) 50 cm (19.6 Inches)
Lesser Amberjack 67.5 cm (26.5 Inches) 50 cm (19.6 Inches)

 Other Characteristics

Almaco jack can further be differentiated by their darker color and their second dorsal fin being much higher than the other amberjacks.

Amberjack Identification
Here you can clearly see that the almaco jack’s second dorsal fin is higher. The first dorsal is not visible in either fish. Almaco jack on top, greater amberjack on the bottom.

Juvenile almaco jacks do not look like other juvenile amberjacks or very much like adults:

Amberjack Identification
Juvenile Almaco jack. Bars are present when fresh. The exposure was lightened on the dorsal fins Intentionally.

Banded rudderfish are slimmer, with a less deep body than other amberjacks.

Amberjack Identification
Greater Amberjack on top has a deeper body. The Banded Rudderfish below, has remnants of bars, and a shallower body.

They are also much smaller, and tend to have a blue sheen in my experience. Up until about 14 inches, they also have either black bars, or the remnants thereof. Please note that pilot fish, Naucrates ductor is another jack that looks superficially similar to juvenile banded rudderfish. The easiest way to tell them apart is to look for the presence of 2 dorsal fins. Pilot fish have lost the first dorsal fin, although rudimentary spines may still be present.

Amberjack Identification
A banded rudderfish with bars fading.
Amberjack Identification
An adult banded rudderfish. Notice the blue sheen, and the lack of bars.

 

Maxilla Comparisons

 

Amberjack Identification
Maxilla and supramaxilla

Lastly, there are two bones on the jaw of the amberjacks, called the maxilla and supramaxilla, that are often cited during identification. For ease of reading, we will refer to both these bones combined as the maxilla, as they are not easily separated visually. The shape of this bone can be used as a method of preliminary identification, but shouldn’t be the only factor used. The greater amberjack’s maxilla is very rounded, with a “boot” protrusion on its dorsal surface. The banded rudderfish’s maxilla is pretty flat across the top, and drops with little curve in what is almost a 90 degree angle. The lesser amberjack’s maxilla does have a bit of curve to it, but no “boot” projection. The almaco’s maxilla is sort of a cross between the lesser and the rudderfish. I seem to be out of adjectives at the moment, but look at the pictures, they say it all.

It is also important to note the position of the maxilla with respect to the eye. Notice how in the greater amberjack, the maxilla reaches to at least the midline of the eye, while the rudderfish and the lesser do not.  The almaco’s maxilla barely meets the front of the eye. Please note that this can vary, especially with younger fish, and should not be the sole factor in determining the species.

It is also important to note the line running through the eye of the fish, towards its first dorsal fin. Known as the “nuchal bar”, when present, it will flow from the eye to well in front of the first dorsal fin in lesser amberjack, and from the eye to the first dorsal fin origin in greater amberjack, almaco jack, and banded rudderfish. This bar can fade with age.

Gill Raker Counts

Gill Arch
Gill Arch Diagram

When external morphologies fail to ID the fish, we must resort to counting gill rakers on the first gill arch. You can do this by simply lifting the operculum (“gill flap”), and start counting all the rakers on both the upper and lower limbs of the first gill arch.

Amberjack Identification
The gill arch of an almaco jack

Once you have counted a few times, and are sure of your count, you can consult this table to help Id your fish:

Common Name Fish Length Gill Raker Count Fish Length Gill Raker Count
Greater Amberjack < 20 cm FL 18-24 >20 cm FL 11-19
Lesser Amberjack < 10 cm FL 23-26 >20 cm FL 23-26
Almaco Jack < 10 cm FL 24-29 >20 cm FL 18-25
Banded Rudderfish < 10 cm FL 20-25 >20 cm FL 12-17

 

The number of gill rakers in the greater, almaco, and banded rudderfish slowly decrease in number between 10 cm and 20 cm. Note that 20 cm is 7.87 inches. The gill rakers in the lesser amberjack remain constant.

As you can see, the greater amberjack, and the banded rudderfish counts can potentially overlap, as can the lesser and the almaco jack.  This is where you will start comparing the other characteristics, in conjunction with the raker counts, to make a positive ID. The hardest fishes to differentiate are the greater and lesser amberjacks, and this chart of raker counts will simplify that for you.

It may help to just check if the rakers extend all the way to the point where the gill arch connects to the fish. In greaters and banded, there will be a space between the last gill raker, and the point of connection, where in the remaining two, the rakers will continue along the arch up until the connection point.

Amberjack Identification
Notice how the rakers extend most of the way to the end of the gill arch. Almaco Jack.
Gill Arch
Notice how the rakers stop well before the end of the gill arch. Greater Amberjack.

 

My methodologies

When I come across one of these fishes, the first thing I do is to check if it is larger than 20 cm. Then I check to see if it is an almaco jack. Remember to look for the high second dorsal fin, the size of the fish, the darker olive coloration, and the maxilla without a boot. If it doesn’t meet any of those prerequisites, then I move on and try to eliminate a banded rudderfish as a possibility. What does the maxilla look like, what is the size of the fish, is there a nuchal bar present, is there a blue sheen? Usually you can knock out both banded rudderfish and almaco jacks without ever lifting the operculum. At this point, you have narrowed it down to either a lesser or a greater amberjack, and it’s time to check the gill rakers. If the raker count is 11 – 19 then the fish is a greater amberjack, if it is 23 – 26, then it’s a lesser. On a side note, the lesser amberjack is a much less common fish, and I have only ever seen a handful.

So there you have it, amberjacks demystified. If you have any issues with your amberjacks, or any other fish for that matter, don’t hesitate to post a question or send an email under the contact us page.

Further Reading:

Greater Amberjack 

Lesser Amberjack

Banded Rudderfish

Almaco Jack

 

SOURCES:

Banded Rudderfish

Robins, C.R. and G.C. Ray, 1986. A field guide to Atlantic coast fishes of North America. Houghton Mifflin Company, Boston, U.S.A. 354 p.

Almaco Jack

Myers, R.F., 1991. Micronesian reef fishes. Second Ed. Coral Graphics, Barrigada, Guam. 298 p.

Lesser Amberjack

Smith-Vaniz, W.F., J.-C. Quéro and M. Desoutter, 1990. Carangidae. p. 729-755. In J.C. Quero, J.C. Hureau, C. Karrer, A. Post and L. Saldanha (eds.) Check-list of the fishes of the eastern tropical Atlantic (CLOFETA). JNICT, Lisbon; SEI, Paris; and UNESCO, Paris. Vol. 2.

Greater Amberjack

Paxton, J.R., D.F. Hoese, G.R. Allen and J.E. Hanley, 1989. Pisces. Petromyzontidae to Carangidae. Zoological Catalogue of Australia, Vol. 7. Australian Government Publishing Service, Canberra, 665 p.

FAO. 2002. THE LIVING MARINE RESOURCES OF THE WESTERN CENTRAL ATLANTIC.
Volume 3, Pages 1434-1435.  8 July 2014.

 

 

 

Read More

Blue Marlin Sampling

A Blue Marlin
A composite shot of a Blue Marlin

 

Ever wonder what becomes of a blue marlin after all of the photographs, interviews, and fanfare of a fishing tournament? How exactly do you dispose of a 900 pound fish?

Blue Marlin
A blue marlin on display.

In order to answer that, I took a camera along to document the process! After all the crowds disperse, the fish is loaded onto a flatbed truck, and moved to a suitable location on the water for biological sampling. Unfortunately this takes a lot of brute force, and there was no time for photographs.

After the fish is removed from the truck, which is by no means an easy feat, sampling can begin.

Blue Marlin Sampling
A blue marlin ready for sampling.

Blue Marlin Sampling:

The goal of this whole project was to harvest tissue samples for various laboratories. These include liver samples, stomach contents, age structures, and muscle samples. Different labs will use these tissues to determine things such as diet, age, and mercury content. In order to access these tissues, the fish must be cut up! Although that may seem obvious, there is a right and a wrong way to achieve this. Cut up incorrectly, you risk damaging the tissues to be sampled,  or, you risk floating 900 pounds of stinking fish into some poor fools backyard who happens to live down current.

Here you can see some organs, including the bubbly swim bladder, which we will discuss later on.

Blue Marlin abdominal cavity
A Blue Marlin’s abdominal cavity

I have no photos of the actual samples being taken, as I couldn’t sample and photograph at the same time. Essentially, they are cut out, and unceremoniously placed into plastic bags, which are then placed into a cooler to be frozen afterwards. The samples will be sent to the various labs after they are frozen for a day.

At this point, the sampling is finished.

Blue marlin Sampling
A Blue marlin after having its organs harvested

Disposal: 

Now we move on to disposal! The fish must be chopped into smaller pieces so that the local sharks and other fishes can finish the job for us. We had to ensure that the swim bladder was completely popped to prevent any of the pieces floating away, and as I said earlier, ending up in someones back yard. This apparently was not always the procedure, however, after a few complaints and phone calls, is now on the books.

 

After this, there is a lot of hosing blood over the side of the dock, and throwing of 15 pound hunks of meat into the sound. The bill and head were collected the next day by the angler so that he could get a mount created. A fair question that I hear from people regarding this process has to do with why we throw away so much meat. On the surface, that is a great question, and although there are some people who love to smoke marlin, they are generally regarded as not safe to eat. This does depend on locality and species, and I have heard that Hawaiian anglers often eat their billfishes. In the eastern US however, the mercury content is deemed too high for safe consumption. In fact, as of writing this, the EPA recommends less than one serving per month for men and 0 servings for both women and children. Then why kill it at all? That is another discussion for another day.

Further reading on methylmercury contamination:

US EPA Page on Methylmercury bioaccumulation

Read More

Parasitic Isopod

I was lucky enough to catch a ride on a commercial gill net boat recently, and while the fishermen were targeting spot (Leiostomus xanthurus), I was hoping to add some species and photographs to our collection. The trip was your typical Core Sound gill net trip, with a few hundred pounds of spot, butterfish (Peprilus triacanthus), kingfish (Menticirrhus spp.), cobia (Rachycentron canadum), spotted sea trout (Cynoscion nebulosus), and what I believe to be a live sharksucker (Echeneis naucrates). Unfortunately the condition of the fish, after 12 hours in the net, made it more difficult to identify than I had hoped. Nonetheless, I thought I would take a side by side shot of a small cobia next to the sharksucker as a way of showing the differences between these two often confused fishes.

 

Sharksucker on top, cobia on the bottom
Sharksucker on top, cobia on the bottom

Turns out that the condition of both fishes was too poor to really help with teaching identification, but while preparing for the shot, I noticed another interesting animal:

 

This is a species of parasitic isopod (think rolly-polly), and although I haven’t the slightest clue as to which species, I can tell you that it plays an identical role to another similar isopod, Cymothoa excis. For the uninitiated, this is a parasitic isopod that attaches itself to the base of the tongue, and then sucks blood from the tongue causing it to atrophy. Once the tongue is out of the way, the isopod then sets up shop, attaches to the stub, and replaces the tongue. From this point onward, the fish will use the isopod as it would its own tongue.

ssmouthside
Parasitic Isopod trying to escape

In the south eastern US, some anglers refer to Atlantic Menhaden (Brevoortia tyrannus) as “bug mouths,” as they are often infected with a similar parasitic isopod.

This particular isopod survived the death of the fish, and attempted to escape. Whether or not it is capable of surviving on its own, I don’t know. However, in case you ever come across one and have the crazy idea to handle it, be prepared, they are not only very quick to latch on, but very capable of biting you too! It doesn’t tickle.

 

Read More