Tips and pitfalls to Fish Identification

[MuskieBait]

Anglers, both novice and experienced, often run into difficulty when a new species is caught and they have no idea what the fish at hand might be.

Especially for the novice anglers, the search for the identity of this unknown fish could be daunting.

This is a guide in an attempt to help anglers learn how to identify fish.

1) Take good pictures!

You can try to describe the look of a fish, but often descriptions can be vague, misinterpreted, misrepresented, misleading, and down right incorrect. A good photograph, as they say, speaks a thousand words. So it is definitely important to take some pictures of the unknown catch. The most useful picture is usually one where the fish is lying sideways on a simple, clean background (like concrete, sand or the ground) with fins completely spread and in good focus. It is important that no part of the fish is obscured or hidden by other objects, shadow or camera flash. I'll explain why later. Often, after laying the fish on the ground, a GENTLE poke of the fish ON THE BACK (NOT the belly!!!) will cause the fish to react and spread its fins. This is a defense mechanism of the fish. Under a predatory attack, the fish being attack will often spread its spiny fins to make it difficult for the predatory to hold the fish in the predator's mouth, or for the predator to swallow it. So you can simply give the fish a poke to induce it to spread its fins.

2) Know the basic fish anatomy!

In most fish identification guide, there will be some description about the physical characteristics of the fish. How many fin rays are present? How large is the gill flap? How many gill arches are there? What is the preoccipital lenght? Almost always there is description of fish anatomy. You should know various types of fins (pectoral, pelvic, anal, dorsal and caudal) and specific parts of the fish (operculum, gill plate, caudal peduncle, adipose fin, etc). Some terms like anterior, posterior, ventral, superior and anterior also helps. These are very specific and accurate terms. When you say posterior of the dorsal fin, it means exactly that - behind the fin above the back - but in a much more accurate and concise fashion. If you ignore these terms, a lot of the fish identification resource is of little use.

3) Use trusted resource!

There are a lot of websites out there, and lots of guides available, that you can find on the internet. Exactly which one to use and which one you should trust can be difficult to determine. In general, avoid guides made by individuals that are not formally published as a book or a proper guide. There is A LOT of garbage out there. The simplest source is guides produced by the fishery department or natural resource department. These guides are designed to be used in a simple fashion and the information is verified for most part. Another source I personally appreciate is FishBase. It takes a little time to learn to use it to its full potential, but you can search for related species and species occurring in a particular region of the world in specific general waters with good ease. In any case, always use trusted source!

4) Overall colouration can be deceptive so trust definitive characteristics!

Often, people will describe a fish by its colour. In some cases, it can be helpful, but in some cases it is completely useless. Depending where the fish was caught, the local habitat and water condition or even the time of year can affect the coloration of a fish. Some Walleye could develop blotches and look like a Sauger. A Lake Trout can develop bright orange fins, an emerald back and yellow spots that resembles a Brook Trout. As such, colouration and patterns can often be deceiving. Instead, there could be definitive features that will more often than not identify a species. These features often include lateral line scale count, fin ray count, shape of tail and fins, ratio of physical features such as distance from tip of snout to the eye or length of dorsal fin with respect to entire body length. These are features that most often do not lie. Last spring, I caught a crappie that for most part looks like a White Crappie with its vertical bar like marking. However, after counting the number of dorsal spines, it was concluded that the number of spines is actually consistent with the Black Crappie. In addition, the length of the head was much longer than a Black Crappie. Given all the characteristics, it is likely the unknown fish is likely a hybrid between Black and White Crappie, since both species are known to occur in the lake and they do hybridize.

5) Consult but don't overly rely on sampling data!

If you search the internet, you can often find fish sampling data for a particular lake or river. Yes, these are often contained in a published reports that are scientific, technical and long. However, there is often no better resource than these sampling data. This data represents fish that had been caught and sampled in a particular location on a water body, and it can serve as a confirmation for certain species that can occur in a certain body of water. You can describe an Alligator Gar to the best of ability and think you have caught one in Ontario waters, but if one has never been sampled in Ontario and the fish is not native (or does not occur) in the body of water you were fishing, the validity of that identification comes under serious scrutiny. You better be expecting a lot of questions and doubts. Now, this is not to say sampling data is completely accurate. The downside to sampling is that the information represent a "snap shot" for a particular time (at the time of sampling) and for a very small location. For example, if the MNR were to sample Rouge River in the summer, they would likely not find any Chinook Salmon in the creek. It does not mean that salmon does not or cannot occur in the creek, since Chinook Salmon does indeed run in the creek in the fall. It just meant that given a certain time of year these were the species that were sampled. Also, sampling could be done in a very specific area with a very specific method. If a large floating gill net was used as the sampling method, perhaps only surfaced oriented species that are large enough to be trapped by the net would be caught, and only those in the area where the net was placed would be caught. As such, fish that hides along shoreline structure may never be caught this way, benthic fish that spend their lives on the bottom may never be caught this way, and certainly fish smaller than the size of the net mesh will never be caught this way. Thus, only trust sampling data to a certain degree.

6) Read, read, and read some more.

There is no substitute to searching and reading all the "credible" information available. Even the best guide may have discrepancies and mistakes. It is best to read various guides and distill some identification features that are consistent between the guides. Trusting only one guide is often dangerous if not naive, but trusting the common feature stated in 10 other guides certainly put credibility for that piece of information. Reading and searching also help your ID skills since you will likely come across pictures and description of other species that you have never known to exist...but now you were exposed to it. Repeated exposure will give you familiarity toward fish overall appearance and characteristics, which will certainly help you narrow down certain family of fish even if you do not know the exact species. Read about various species even if you may never catch them. Knowledge is power!

7) Know some basic family of fish and their general shapes.

Fish belonging to the same family often look similar. Sunfish species share similar body plans. Same can be said for the Trout and Salmon species. Same can be said for the Catfish family or the Minnow family. Once you have an idea which family the unknown fish belongs to, the guess work is drastically reduced. Saying this, it is very important to know the relatedness of species and their species tree (or phylogeny tree) which shows how closely related various species are to each other, and how these species are arranged and organized.

In short, sure, you can always post a picture on the forum to ask for an ID, but it is simply reliance on secondhand information that may or may not be correct. I have read some terrible ID before where a person is completely convinced he/she is correct on identifying a species, but their answer was completely incorrect. False information can affect you if your catch was out of season or have closed season, or if the species was endangered or it is an invasive species. As such, it is ALWAYS best to build YOUR OWN fish identification skills and TRUST YOUR OWN JUDGEMENT!

I hope this guide helps.

[OldTimer]

It does help and you bring up very good points........... particularly point 4 re colour.

Thanks.

OT

[OldTimer]

I finally had time to investigate the FishBase site you mentioned.

Impressive!

http://www.fishbase.org/search.php

OT

[MichaelAngelo]

(05-31-2013 06:36 AM)OldTimer Wrote:  I finally had time to investigate the FishBase site you mentioned.

Impressive!

http://www.fishbase.org/search.php

OT

Fishbase is quite impressive. Sometimes I find incomplete entries. What I find helpful is to google the fish I want to ID and then "similar species", it points me towards resources that explain how to differentiate similar fish.

For example I google

fathead minnow "similar species"

To learn that the bluntnose minnow looks very similar to fathead.

Ken also has a neat trick on Fishbase to discover which similar species of fish can be found in a particular area.