What is a stock assessment? Part I

Introduction

Assessing in style

           Stock assessments are an important part of the way we manage fisheries in the U.S. A lot goes into a single stock assessment, and they can be quite daunting to navigate. However, when you break them down into their component parts they really aren’t so bad! In this post we will begin to explore stock assessments by introducing the concept and talking a bit about the process involved with stock assessments in Federal waters (*in Florida, marine waters past 3 miles offshore in the Atlantic and past 9 miles offshore in the Gulf of Mexico are governed by the Federal government through NOAA’s Fisheries branch, and waters inshore of that are governed by the State through the Florida Fish and Wildlife Conservation Commission; they also use stock assessments, and we will tackle their management process in a future post).

Background: what is a stock assessment?

At its heart, a stock assessment is simply what it says: a project aimed at assessing a stock of fish. The term “stock” simply refers to a unit of fish that is being managed. The unit might be distinguished based on biology or fishing practices. For example, in the state of Florida our fish species are often divided into Atlantic and Gulf of Mexico stocks because few fish travel between the two bodies of water, so we consider them separately. A stock assessment pulls together all of the available information on that stock, including biology and information about fishing, to try to figure out both what is going on with the stock at present (Is it overfished? Is it doing just fine?) and to predict what will happen in the future (What about 10 years from now? Can we keep fishing the same way?).

Grouper are one example of species assessed using the SEDAR process

Stock Assessments in the South: the SEDAR process

SEDAR (short for the “Southeast Data, Assessment, and Review”) refers to the way Federal stock assessments are conducted in the Southeastern U.S. The process consists of three workshops: the Data Workshop, the Assessment process, and the Review Workshop. During the Data Workshop, fisheries scientists pull together all of the data, or information, that will be needed for the stock assessment. Next, researchers use this information to create the stock assessment models during the Assessment process (*we will talk more about models soon). Finally, a group of different experts review everything during the Review Workshop. The completed assessment (including all three reports from the workshops) are then sent to the appropriate Fisheries Management Council’s Scientific and Statistical Committee to be accepted as appropriate for management. The Committee then uses the information in the assessment to make management recommendations, which go to the Fisheries Management Council (in Florida, this would be either the Gulf ofMexico Fishery Management Council or the South Atlantic Fishery ManagementCouncil). The SEDAR process is certainly complex and involved, but it helps ensure that the stock assessments are of the highest quality and therefore that the management recommendations we get out of them are the best possible.

Stock Rebuilding Targets: Biological Reference Points

            If a stock has been assessed as overfished (meaning that too many fish were caught in the past), the Sustainable Fisheries Act (*a National Act passed by Congress) mandates that managers create a “rebuilding plan” for the stock to get it back to sustainable levels. To do this, managers have to aim for a target, or “biological reference point”, that lets them know that the stock has returned to sustainable levels. There are many different types of reference points, and we will explore them in detail in another post.

Next time: what all goes into a stock assessment? 

*Want to learn more? Check out these handy resources:

NOAA Assessment 101

Ode to Batfish: Biology in Verse

Oh batfish, oh batfish of the briny deep

On modified pectoral fins you creep

“Walking” along the benthic sea floor

Of all the fishes, it’s you I adore

Your rostrum projects like a unicorn snout

While your dorsal fin spine above you pokes out

You wave it about to attract your prey

Like an undersea angler, or so they say

Dorsoventral compression makes your body shape flat

Thick fins project sideways, like the wings of a bat

Often your skin is bumpy and brown

Though some colorful species remind us of clowns

Large head, in a circle or triangle shape

With a tiny tail, you assess the landscape

Your beauteous lips in an eternal pout

Eating worms, fish, crustaceans is what you are about

Some species reside in shallower seas

While others crawl in the deep with ease

Tropical and subtropical oceans you span

And I will always be your biggest fan

Some say that you’re ugly, some say that you’re strange

But there’s nothing about you I would willingly change

Oh batfish, oh batfish who dwells in the sea

My favorite fish you will always be

————————————————————
For more on the batfish (aka the coolest fish ever):

http://www.fishbase.org/summary/FamilySummary.php?ID=194
https://www.flmnh.ufl.edu/fish/Gallery/Descript/BatFish/Batfish.htm

And check out these batfish videos!

Seagrass Savanna

Check out this video detailing the work of graduate student Savanna Barry, who studies seagrass along Florida’s Gulf coast:

//player.vimeo.com/video/116519146

Seagrasses are an important part of our coastal systems and perform many important and valuable ecosystem functions, such as providing food and habitat for a number of marine fish and invertebrate species; it’s estimated that somewhere near 70% of Florida’s fishery species spend at least part of their life cycle in seagrass communities. Seagrasses also help maintain water clarity, and their roots and rhizomes stabilize coastal seafloors. Clearly seagrasses are important coastal habitats, and it is therefore unsurprising that the Florida Department of Environmental Protection (FDEP) estimates that each acre of Florida seagrass has an economic value of approximately $20,500/year!

For more on Florida’s seagrasses visit:
http://www.sms.si.edu/IRLspec/Seagrass_Habitat.htm
http://www.dep.state.fl.us/coastal/habitats/seagrass/
http://myfwc.com/research/habitat/seagrasses/information/importance/

What the heck is that? On sea robins and their awesomenitude

Florida is home to an incredible diversity of fish species, so it is unsurprising that every once in a while something weird comes up on an angler’s hook. Most of us can easily identify the common species, like snook, redfish and trout; but what would you say if you got this guy on the end of your line?

Answer: “Awesome! A sea robin!”. Sea robins (also called gurnards) live all over the world in tropical and temperate waters. Sea robins like to hang out on the bottom, though they do swim through the water column from time to time. There are many different species of sea robins, at least 7 of which are found in Florida waters.

Sea robins have hard bony heads, but what really makes them cool are their pectoral fins: the lower three fin rays are modified to form what look like fingers, which they use for support and to search for food. Check out this youtube video to see them in action as they “crawl” across the seafloor:

https://youtube.googleapis.com/v/qU7hmwzuQ1k&source=uds

Sea robins are also known to vocalize, or make drumming or croaking sounds. Fish use many different methods to produce sounds, depending on the species. Some make noise by grinding their pharyngeal teeth together (pharyngeal teeth=teeth located in the pharyngeal, or gill, arches of fishes). Others, including the sea robin, have a special muscle which they vibrate against their swim bladder to make noise; this is the same method that drums use to vocalize. Check out this video to hear some sea robin vocalizations:

https://youtube.googleapis.com/v/E9JfjNb8S4E&source=uds

In the state of Florida, there is very little targeted fishing for sea robins, though leopard sea robins are sometimes caught commercially for bait or for the marine ornamental trade (for use in aquariums). For the most part, Florida anglers don’t target sea robins, but that doesn’t mean they don’t occasionally catch or snag them, so they still come up on lines from time to time. They can also be seen while diving or snorkeling, as many species inhabit shallower waters. So keep an eye out for sea robins next time you are on or in the water!

For more on sea robins see:

Fishbase:Triglidae

FAO guide

FWC leopard sea robin regulations

Climate Change and Florida’s Fishes

We’ve all heard about many of the potential impacts of climate change, such as the polar bears losing their habitat or the melting of the polar ice. But what will climate change mean closer to home? How will it impact our marine habitats and the fish that live there? Check out this video for an overview:

//player.vimeo.com/video/103328171

Climate Change and Florida’s Fishes on Vimeo.

This is just a brief glimpse at climate change and it’s potential impacts on fish and fishing in our state. For more details on climate change and ocean acidification, check out the IPCC (Intergovernmental Panel on Climate Change) Reports, UF/IFAS’s EDIS report on the Economic Impacts of Climate Change in Florida, or check out the references below.

Some References: 

1. Alongi, D.M. 2008. Mangrove forests: resilience, protection from tsunamis, and responses to global climate change. Esuarine, Coastal and Shelf Science 76:1-13.

2. Cheung, W.L,, J.L. Sarmiento, J. Dunne, T.L. Frolicher, V.W.Y. Lam, M.L.D.Palomares, R.Watson, and D. Pauly. 2012. Shrinking of fishes exacerbates impacts of global ocean changes on marine ecosystems. Nature Climate Change 3:254-258.

3. Diaz, R.J. and R. Rosenberg. 2008. Spreading dead zones and consequences for marine ecosystems. Science 321:926-929.

4. IPCC Working Group I. 2013. Climate change 2013: the physical science basis. Summary Report for Policy Makers IPCC WGI SPM AR5: 33 pp.

5. Mumby, P.J., A.J. Edwards, J.E. Arias-Gonzalez, K.C. Lindeman, P.G. Blackwell, A. Gall, M.I. Gorczynksa, A.R. Harborne, C.L. Pescod, H. Renken, C.C.C. Wabnitz, and G. Llewellyn. 2004. Mangroves enhance the biomass of coral reef fish communities in the Caribbean. Nature 427:533-536.

6. National Research Council. 2012. Climate change: evidence, impacts, and choices. National  Academy of Sciences. 40 pp.

7. O’Brien, C.M., C.J. Fox, B. Planque, and J. Casey. 2000. Climate variability and North Sea cod. Nature 404:142-143.

8. Pinsky, M.L., B. Worm, M.J. Fogarty, J.L. Sarmiento, and S.A. Levin. 2013. Marine taxa track local climate velocities. Science 341:1239-1242.

9. Roessig, J.M., C.M. Woodley, J.J. Cech Jr., and L.J. Hansen. 2004. Effects of global climate change on marine and estuarine fishes and fisheries. Reviews in Fish Biology and Fisheries 14:251-275.

10. Rose, .A. 2005. On distributional responses of North Atlantic fish to climate change. ICES Journal of Marine Science 62:1360-1374.

Michael and the Peppermints II

Hey all! A while back I posted a teaser and promised a video on UF graduate student Michael Dickson’s peppermint shrimp work; here it is! Woo! Presenting….. Michael and the Peppermints 

//player.vimeo.com/video/85529079

Michael and the Peppermints on Vimeo.

Do bananas mean bad luck fishing?

Ok team, today I am going to stray a bit from my video posts to talk about a very important topic: the bad luck bananas are thought to cause to fishing expeditions.

The question: Do bananas really bring bad luck to a boat?

Background: Where does the taboo come from?

        There are many theories as to where the “bad-luck-banana” superstition got started. Some people think it began back in the colonial shipping days, when trade vessels brought bananas from the New World across the Atlantic to Europe. Bananas spoiled quickly on board the boats, and so the ships had to travel fast; this pressure on speed may have led to riskier and more disastrous voyages. Alternately (and less sadly) the speed also meant that the boats had less time to stop and fish, which may have led to the association between bananas and low fishing success. 

image from: http://farm4.static.flickr.com

       Other theories focus more on the cargo than the voyage. Historically, creatures like spiders and snakes would stow away in banana cargo, and so it may have been that captains started the rumor to keep banana crates off their boats. Another theory is that because bananas give off ethylene gas as they ripen, they may have caused other food to spoil quickly in the cargo hold, resulting in their unpopularity on boats. One story from Hawaii says that bananas packed by fishing tribesman would spoil at the same time that the men paddled too far out for good fishing, hence their association with poor fishing.

Whatever its origins, the banana taboo is here to stay in angling culture; some fishers even extend the taboo to include anything associated with bananas, such as banana boat sunscreen or banana republic clothing. I for one have many friends who would be exceedingly angry were I to sneak a banana on board their boat, and anecdotes relating bananas to poor fishing days abound in Florida. So when as a student I was asked to design a study for a course I was taking, it seemed the time was ripe to set the records straight.

The Design: How do we test it?

      To test this study I first needed fishers, so I recruited the help of two awesome volunteers (thanks to Mike Crandall and Geoff Smith). Each angler was given a 5’6″ fishing pole, a bag of hotdog bait, and a kayak. The fishing took place at Watson’s pond, conveniently located at the University of Florida’s Fisheries and Aquatic Sciences center (aka my work backyard). On the back of each kayak sat a cooler, labeled either “A” or “B”; cooler A contained 4 bananas, while cooler B contained bottled water (this was our control cooler, and was filled to make sure the weight was the same so that the guys fishing didn’t know if they had the bananas or not).

Watson’s Pond, the anglers and their coolers (treatment and control)

The great cooler-switch

Testing Begins: Let’s fish!

    At the “go”, each willing dude fished from his kayak for 15 minutes. After the 15 minutes were up, the coolers were switched, and the anglers fished for another 15 minutes. We did this whole set 2 more times, for a total of 3 runs (6 trials overall, with 3 for each fisher).

Results: What did we find?

   Crazily enough, the results from this study do suggest that bananas are associated with lower fishing success! In fact, in 5 out of the 6 treatment blocks more fish were caught with the control than with the bananas. When statistical testing was applied (in this case, what is called a paired t-test), the difference between bananas and no bananas was significant. (Note: we also counted “bad luck” occurrences, things like losing a fish or a hook, as well as compared fish size, and none of these was different between the two treatments).

Results!

Discussion: So what does this mean?

     So does this mean the superstition holds true? Are bananas actually bad luck on boats? Well, we can’t really say for sure yet. This study ran only 6 trials, which is an extremely small sample size, and I for one am not ready to give up my bananas. It may be that if we repeated it again with more trials, or for longer fishing periods, we would no longer see a difference. What do you guys think? Any volunteers?

Image from: http://c3.ac-images.myspacecdn.com

References:
 

Brincefield, J. 2008. The story of bananas and bad luck. Chesapeake Bay & Atlantic Ocean Charter Fishing. Available: http://www.azinet.com   /captjim/bananas.htm. (October 2010).

Gillman, R. 2010. Bananas legend. Nobananasfishing.com. Available: http://www.nobananasfishing.com/bananaslegend.html. (November 2010).

Phillips, A. 2006. Forbidden fruit. Washington Post. Available: http://www.washingtonpost.com/wp- dyn/content/article/2006/06/03/AR2006060300185.html. (November 2010).

Ronca, D. 2008. Why are fishermen superstitious of bananas? How Stuff Works. Available: http://people.howstuffworks.com/fishing superstition1.htm#. (October 2010).

Roldan, J. 2010. So what about those bananas? Available: http://www.tailhunter- international.com/bananas.htm. Accessed November 2010.

How Old is That Fish?

Ever wondered how old a fish is? Check out this quick video to learn how scientists age fish and why it is important:

Now it can get more complicated than this depending on the species you look at (particularly with tropical fishes, which don’t undergo those strong seasonal temperature changes, or with fish that get to really high ages), but that is the general idea!

Wanna try it yourself? You can play NOAA’s interactive fish-ageing game at: http://www.afsc.noaa.gov/refm/age/interactive.htm

Wanna learn more? Here are a few links:
    http://www.marinebiodiversity.ca/otolith/english/age_validation.htm
    http://myfwc.com/research/saltwater/fish/age-growth-lab/aging-fish-otoliths/
    http://www.cefas.defra.gov.uk/our-science/fisheries-information/ageing-fish.aspx
    http://fishconnectivity.cbl.umces.edu/research/otolithmanual

Michael and the Peppermints

We are working on a video series profiling fisheries scientists in action *to be posted soon*, so as a teaser we’ve put together some clips from a recent sampling trip with UF graduate student Michael Dickson. Mike is working on the population dynamics of peppermint shrimp (a species popular in the aquarium trade) and samples monthly aboard commercial shrimping vessels in the Gulf of Mexico. Enjoy, and more to come on Mike and others’ work!

Otolith Shape and Fish Movement

Hey there fishheads!

So as we learned in Joy’s post on the FACT array, tracking fish movements is an important part of fisheries science. In particular, it is important to know whether fish from different places are mixing or remaining geographically isolated (why? see below); however, this can often be a tricky thing to figure out. With this in mind, today I want to introduce a method I think is pretty darn cool…(cue drum roll)…otolith shape analysis! Now, for anyone who may be thinking oto-what now?, fear not! First, watch this handy 1:30 video, and then we can all share in the excitement-

Awesome, right? As a technique, otolith shape has been used to look at stock structure in a whole variety of different species, from goatfish to cod to king mackerel down here in Florida. I used otolith shape in my master’s degree to look at stock structure of greater amberjack in the Gulf of Mexico (results coming soon). Now, otolith shape analysis doesn’t always work or lend conclusive results (as can happen with any scientific method), but it is a nice technique that can be used to supplement tagging or genetic analysis methods, and as it is relatively simple and inexpensive (once the otoliths are collected, the analysis is essentially free), it can be a quick first step into examining stock structure. 

Ok, so you may be asking why geographic connectivity matters in the first place…Well, imagine that a species is fished much more heavily in one location than another; if these two regions are not mixing, then you could end up with localized overfishing (which is never a good thing). Furthermore, different stocks will often have different patterns of growth and recruitment, and so may need to be managed differently. Therefore, determining stock structure patterns is crucial to the sustainable management of our fisheries resources.

If you are interested in learning more about this and other neat uses of otoliths, check out this website by Campana’s otolith research lab: http://www.marinebiodiversity.ca/otolith/english/hot.htm, or the Aforo database at: http://www.cmima.csic.es/aforo/. Or just google scholar otolith shape analysis and check out the numerous studies utilizing this technique!