Newly Published Post-release Shark Survivability Study

[Tightlines667]

For those who might be interested...

There is a Newly Published Post-release Shark Survivability Study that suggests that many (10-25%+) sharks that are released following catch and release fishing may suffer from delayed mortality.  

This study was performed by one of our nations top warm-water marine biological research institutes and published in a reputable scientific journal.  Keep in mind that it is only one if many that have been done over the last 3 decades or so.

Here's the abstract:

http://www.int-res.com/abstracts/meps/v496/p207-218/

And a related article:

http://www.sciencedaily.com/releases/2014/01/140130141315.htm

[Chris Gatorfan]

I think that story is a little bogus, as I have read it myself. IMO Catch and release has worked for many years. And as for the sharks I have not seen an issue with it here in our area and believe me there are AAAALLLLOOOOTTTTTT of sharkers here in my area. Heck My friend LP caught 98 this past year from Land and then another one of my friends runs a shark fishing charted service out of Pensacola and lets not even consider the rest of us guys that do it.
I understand the changes that happen within the sharks body, but believe that with the use of proper catch and release techniques that they all stand a better chance of surviving. Like with us here we let the shark pull away from us when releasing them instead of just tossing or dragging them back in the waterand we try not to have them out of the water longer for 1 1/2 minutes. We make sure our team has everything ready and at to go so we can release them asap.
With the amount of beach goers, fishermen, and boaters here in our area we would be seeing evidence of these high mortality rates. But it yas yet to be seen here. Our fish kills come from lack of oxygen in the water in the dead of summer or from extreme temperature drops. Again this is just my opinion from what I have seen from across the 250 miles of coastline I have fished over the years.

[Tightlines667]

Admittedly that was my reaction as well.

The scientific and management community needs to make sure to continue to be highly skepticle and questioning when examining this stuff.  These studies are just one of many things that need to be taken into account when looking at the overall picture.  I think the actual post-release survivability rates can vary widely depending on many factors.  To me the important thing to be gleaned from this type of data is what physiological factors contribute to stress-induced mortality, and the clear differences that exist between different species (due in part to measurable physiological differences).  Managers need to have 'hard data' and studies that they can point to in order to ensure these types of factors are taken into consideration when developing policy and practices.  They should typically er on the side of caution and never take just a single set of results at face value. 

Regardless of whether or not one agrees with the results these type of targeted studies, typically address a perceived issue that either may not have been adeqetly enumerated, or to add to a body of work.  Conflicting results, or discrepancies often times point out inadequacies in methodology or data sets.  Many of the modern tools available to fisheries research biologist (in this case PSAT tags) are expensive and as such will limit limit overall sample size.  These sophisticated tools can tell us a great deal about a few individuals, but we need to keep in mind that these are just a few individuals... any actual application of mortality rates into the analysis of say population assesments or bycatch  models can only be made if it is based on studies that have adequete sample sizes, have stood the test of time and scrutany, and are proven to be directly applicable to a given population, species, or methodology.  Unfortunately, many decisions are based, in part, on 'best available' scientific data for which it may not end up being very good at all.  I think this study and others like it simply point out that post-release mortality can occur (there may be differences between species), and should be considered. 

I have always felt that managers can learn slit from the fishermen themselves that are actually in a position to bring direct experience to bear. 

Fishermen and the shift in attitudes in recent years need to be highly commended.  They are the ones that are actually making a day to day difference in the conservation if the resources they value. 

When I was a kid we used to kill all sharks that we caught since they were considered a nusance, which drove away our target species, competed with us for the resource we were targeting, and often times stoll or damaged the fish we worked so hard to catch.  But over time, our attitude shifted and we started to respect these predators, and developed means of removing our gear before releasing them.  At the time, we would actually put a nose around their neck, pull their head outta the water to control them, and their mouth, and remove our hook with a pliers. 

Anyways I just thought I'd share the fact that this most recent study was performed, and published.  The management implications surrounding it are yet to be determined.

[Shark Hunter]

I have to agree with Chris on this one. These kind of reports are bad for our sport. Look at the Apex Predator tagging program. There are many sharks caught again over and over. Especially Lemons. I realize some fish do die, It the nature of the sport, bur as far as being endangered, I really think this is a myth as well. If you have ever seen an aerial view of Florida's beaches during the Migration in May. It is astonishing! Shark Fishing is a sport that most people are just plain scared of. I really think that's why Shark Attacks are on the rise as well. Where Shark Fishing is Banned, their only population control is cannibalism.

[Tightlines667]

As a side note...

My personal experiences with shark fishing indicate that they are very hearty, resultant animals that can 'take a lickin and keep on tickin'.  On commercial gear, I have seen sharks survive what would be considered 'horrific' injuries and come back to be recaptured from 1 to severel days later.  Also, I've seen a number of sharks caught withassive wounds that have healed over.  Like I said everything needs to be taken with a grain of salt.   

[Shark Hunter]

Grain of Salt taken. You are a smart Man John!

[saltydog]

I do know that research in and of itself is driven by funders and colleagues, to either bolster an opinion or a position in which one stands. In todays times of corporate and personal agendas a lot of so called scientific research is corrupted to fit where the person funding it wants it to stand. Now with that said, I did attend university studies in the marine biology field so I do know a little about the agendas pushed by not only governments and corporate entities but also by individuals bent on making everyone bend to there way of thinking.

Now with that out of the way the one thing in the report I do agree with is that Hammerheads do die more often when captured due to there willpower not to come in until almost dead from exhaustion. They are one shark that bulldogs to the end. And some of it has to do with the way they are treated when landed. A good way to decrease mortality of sharks is to not fully drag them onto the beach out of the water, I know it makes a great pic but it can on a large animal put undo stress on the internal organs of the fish causing irreparable damage and death. Have your landing bag near, tag in the tag stick, tape in your pocket and cameraman ready. Get that fish de-hooked, tagged, measurements, pic taken as fast as humanly possible then walk the fish out until it swims away. This should all be done within one minute. Then backslap, brag, fill out tag card and do all your other things you would have normally done while the fish is on the beach waiting for you to get your act together.  

Now I am one of those guys that does on occasion take a shark home for the grill but those are mostly 3 to 6 foot BT, the rest go on there merry way with a tag in there back to get caught by someone else a few years down the line. I have tagged several Hammerheads and all of them swam on there merry way with no sign of stress but handling at the end has a lot to do with that.

[Ron Jones]

with the use of proper catch and release techniques

I think this is an important point, and it would be really hard to convince me that their isn't a large percentage of people catching sharks who don't even realize that such techniques have been developed, much less care to use them. It would be unreasonable to believe that the energy invested in developing these techniques don't decrease the mortality rate, but at the same time it is unreasonable to believe that inproper release methods aren't detrimental to the mortality rate. I remember in the 70s we were told (by jauk cousteau no less) that catching sharks causes internal damage so severe that it wasn't reasonable to expect survival. Based on the three points I've presented a scientific organization proposing a mortality rate of 10-25% does not seem unreasonable. I certainatly don't have the education background to question the concept of delayed mortality.

Ron

[Dominick]

Knowing nothing about the subject I am going out on a limb to comment here.  I do not know if the study that was done looked at the delayed mortality of the sharks that were cannibalized.  Here's my thinking.  It seems to me that the study said the delayed mortality was mostly caused by the physical stress on the fish.  In other words its wounds and buildup of lactic acid.  I want to posit that when an exhausted fish is released it will emanate the electric current of a wounded fish.  Indeed it may be trailing some blood from the unhooking.  This leaves the released shark vulnerable as prey for its brethren.  Whereupon the shark is attacked and eaten by other sharks.  Am I wrong here?  Dominick

[Chris Gatorfan]

I would say yes and no Dominic. yes the blood is an attractant for the sharks and does cause the to want to attack the blood source, but thats not always so. I have been on the pier with bloodied up water from Bonito, King Mack, and Spanish Mack, with fish still coming over the rail and anywhere from 3-15 sharks cruising around us and not a single one tried to attack any of our incoming fish. Heck We normally have to worry about the Dolphins eating our King and Spanish Macks more than we do the sharks.

[Tightlines667]

Post release survivability of fishes and sharks is in many cases affected by predation effects on tired, weakened, or injured animals (that may have resulted from capture), and most times these are accounted for in the mortality estimates.  However, It is important to look at how the researchers accounted for this.  If PSATS are utilized as the primary instrument (as is the case here) these tags can not, pop off of the animal, and float to the surface if they have been swallowed by another animal (so it could produce false positive mortality), or conversely they may pop off prematurely as a result of a predation event (though its difficult to determine if this resulted from poor tag placement/retention/natural shedding, tag malfunction, or some other factor in all cases this 'type' data must be accounted for during analysis.  Other typically problematic Post-release research tools include the use of active radio transmitters to track a given animal following release.  Sometimes a predation event may lead to researchers tracking the animal that did the predating, rather then the target individual since he has now acquired the active tag.  Other times there are clear behavioral changes that indicate different phases following release (I.e. recovery period, transition to 'normal' expected movement/dive patterns), and other times mortality events are clear..the animal stops moving and sinks to predetermined release depth or bottom.  Researchers will outline whether data anomalies are excluded from sample analysis, or assigned a mortality factor (based on probability), or are treated in some other fashion.  The point is Natural tag shedding, and predation events must be accounted for or they can skew the results, ESP. W/small sample sizes.  Some species are particularly prone to these issues w/ tag-recapture, and post release behavioral studies, locality and temporal characteristics can also come into play.  For instance, a post-release survivability study on GTs caught on sportsfishing gear within a refuge where there were significantly high levels of aggressive sharks and other predators in the immediate vicinity during release showed high post-release mortality due to predation events.  The sharks targeted the recently released fish in their 'weakened state, and became more adept at cuing in to them.  Other times surprising results, like a negative feed response from sharks in the immediate vicinity of their breathern being released (or killed) are observed.  Studies which take place over a larger area and time, along with greater sample sizes tend to parse out these relatively rare outliers and produce better results.

Either way it's a good point.

[Jeri]

Hi Guys,

A little background to put my opinion into perspective. I spent 12 years involved in shark conservation in the UK, and part of that time developed and then ran the UK shark tagging programme. I attended symposiums all round the world, and even eventually presented a paper at one of those concerning fisheries in the North Atlantic.

Running a tagging program, post-release shark mortality was of huge interest, and something that we studies hard from all the available papers and figures available at the time. We were especially considered with some scepticism by the 'scientific community', as we solely used recreational anglers as our sources of information and taggers – in their minds 'dirty data', but with appropriate formulae, we could tune out all suspect data, and void their concerns.

This brings to the point that scientists are resistant to those who are not scientists, and anything that they say, as you aren't a member of their 'castle in the sky club'. Added to that we soon learned to listen to all the papers presented at various symposiums with an ear towards what are their background agendas. There is a huge reserve of monies out there for anyone looking to discredit recreational angling, and promote tree hugging.

Back to this particular paper, the point that lactate poisoning occurs is not new, the longer the fight the higher the potential levels, the longer the recovery period – this is old new, even 15 years ago, this was proven. In some species, and this study only covered 5 coastal species, there are another 400 species to look at for this particular scientist – before he can make any real assumptions on post-release mortality.

They used recreational anglers for their sampling method, and did use either their own long lines or commercial fisheries, so the sampling is 'skew'. They come out with global statements about the vulnerability of sharks globally, but fail to highlight that the contribution to that threat by anglers is infinitesimally small, as by far the greatest predation on sharks is by commercial fishermen, who rarely release sharks.

The fact that recreational anglers over the past 30-40 years have started to rapidly increase the proportions of their catch that they release is obviously ignored – for it would 'skew' their assumptions of blame.

Like all these 'scientific papers', they need to be read with interest, for they might have something that we can all learn, but that tiny gem stone is buried way too deep in their information, as it might actually detract from the outlandish assumptions that they are proposing.

What shark anglers do need to encourage and develop across the globe, is better shark handling when they have caught their quarry, the mere fact that we are all going down the road to wanting to release is a good first step in a very long road – but the following steps of handling and revival are equally essential. Even here in Namibia and southern Africa, we need huge advances in our shark handling, and something that I will be taking to a meeting this coming weekend.

If the scientists wanted to do something useful, rather than shoot from the sidelines, they should come on board with the angling community and help us develop better handling practices – but then we probably don't pay as well as tree huggers?

Just my thoughts!



Cheers from sunny Africa


Jeri

[Ron Jones]

Jeri brings up a great area of discussion yet to be broached here.

I've caught maybe a dozen or more species of sharks in my life. One thing I can say with certainty about them is that they are different. A spoon tail sand shark is not a mako. A thresher is totally different to a tiger. If someone came to me with anything less than the word of God that they all recover the same from being caught I'd call that man a liar. The species and habitats are just to varied. The size of gear and methods used are all over the map. A big bull pulled in fast with a 12/0 bolted to a broomstick has experienced a totally different level of trauma then a 100 pound mako caught on a surfmaster and fought for hours with a fern stem (my preferred method, by the way). The release method varies...etc.

While the percentages quotes still seem reasonable to me I do not agree with their science.
Ron

[Jeri]

Hi Guys,

Post-release predation is potentially an issue, especially where smaller sharks are released, or smaller species, as obviously some of the smaller species are 'on the menu' for larger species – sharks do eat sharks.

There are literally thousands of variables that may or may not come into the equation of this whole issue, water temperature, depth, oxygen levels, turbidity, local terrain, etc, etc, the list goes on as well as the obvious potential problems of lactic acid issues as well as possible minor things like methods caught, and the whole host of handling issues.

There are studies that offer a time of recover as little as 20 minutes for some pelagic species, where high oxygen levels are apparent – though in that study those variables were not taken into consideration – basically available oxygen to offset the effect of lactic acid in the blood make up. As all the sample species in this particular exercise were large coastal, where oxygen levels would have been as much as half as when considering pelagic species.

This all starts to tend towards the fact that while some of the results obtained by this researcher may well be accurate, they have to be expressed in seriously the right context, not some précis of the actual results.

On the other issues of 'blood' from wounds, this is conceivable, but more importantly is the actual issue of scent. Here in southern Africa, we do still get a lot of anglers using whole fish as bait for sharks, but recent developments have found that smaller – high scent baits work equally as well, and are by far easier to use.

A typical example is when fishing for one of our smaller species (Spotted Gully shark) we find that a bait made up of gills frame and the liver of a smaller edible species is by far more effective than any whole bait. There is this overwhelming fantasy about 'sharks and blood', which in reality has more to do with scent, rather than blood, hence the liver content to the bait. Blood soon washes out, but a punctured liver section, will ooze oils out for a lot longer period. This 'scent trail' is what the sharks follow down to get to the source, and then eat the bait.

Sure there are issues like smaller fish pecking at a cut bait, but they wouldn't be doing it in the case of a whole bait, if the sharks were soon on the bait, due to the 'scent trail' drawing them in quicker.

It would be interesting to see the difference in performance between a whole bait and a slab bait (with liver), when fished side by side, which would attract the attention of sharks quicker?  - Something for you guys down Florida way???

Back to the 'dodgy scientists' and their grand statements – someone suggested a serious pinch of salt – this is probably the right way to approach this sort of global statement, as the guy obviously has another agenda. The tree huggers have identified that it is easier to discredit anglers than try to discredit commercial factors, as obviously their attempts at dealing with one of the biggest global issues surrounding sharks – finning, has had little effect, so now switch to something that is easier to challenge, and left finning carry on beyond the horizon.

Just my thoughts!



Cheers from sunny Africa


Jeri

[saltydog]

It would be nice if NMFS would get on the issue at hand and start to really look at the real issue of shark mortality, commercial shark fishing. Finning is the #1 reason for mortality issue in the shark fishery today, and governments seem to turn a blind eye towards it. It is time for the world community to take a hard stance on this issue instead of dancing around it but I know it will never go away. Heck look at whaling, they are still killing them for there meat, and the world just stands by and lets it happen.
It is all great to talk about the issues but it would be nice if the real issues would be handled, commercial fishing. You want to save the Bluefin tuna, stop all commercial fishing for 10 years and see what happens. Just like snapper fishing for red snapper in the Gulf of Mexico, they give us some short restrictive seasons for recreational limits but millions of pound are caught for the commercial industry, who is the real problem? Yes I used to be a commercial fisherman and I do see where it would put some people out of work, but hey that's what they did to my way of life when they decided to ban the nets in the gulf, so it can be done, why don't they do it. Those are the questions that need to be asked.