Epic Goliath diving and more deaths +

[Reef_Haven]

As I said above, the age structure of the population is critical in determining SPR and federal law mandates that determination. There are only 2 alternatives for getting age structure from the goliath grouper population: 1. take fin rays and let the fish look "mutilated" for about a year, or 2. kill 800 to 1000 goliaths to sample otoliths (ear stones) which are located in the brain. We are aware of no other alternatives. We choose to keep the fish alive so the ecotourism trade can benefit from these spectacular animals.

The reason why we are sampling in your area off PB and Martin Counties is because that is the spawning area for the Atlantic coast of Florida. We have documented the fish traveling over 200 miles to get to your area just prior to the start of the spawning season in August. If we sample there, and during the spawning season (Aug and Sep) we will have a representative sample of ages from the entire region. Spawning is winding down now, so the fish should be moving back to their home sites soon.

[/I]

The problem with surveys is the data can be skewed towards any desired result.
Surveying a spawning area, and believing it will provide the representative sample of all ages in a population is like taking a survey at a strip club to determine the percentage of adults in a city.

 

[Amazz]

While certainly not happy, I wouldn't count the fish in the video as dead yet.

I found it dead the next day. Same fish, same location. Definitely dead and decaying.

 

[smellzlikefish]

Touche.

 

[danvolker]

The problem with surveys is the data can be skewed towards any desired result.
Surveying a spawning area, and believing it will provide the representative sample of all ages in a population is like taking a survey at a strip club to determine the percentage of adults in a city.

I asked Sarah to address this....

Sarah Frias-Torres	3:08 PM (3 hours ago)		​
to me

OK Dan, here it goes.

To understand the age structure of a fish population, juveniles and adults must be sampled. In the case of goliath groupers, juveniles (less than 120 cm total length) are found in mangroves. Adults are found in coral reefs, reef ledges, rock reefs and wrecks. In addition, goliath groupers form spawning aggregations where the entire breeding population in the state of Florida is concentrated in just a few locations. When you have a species that uses different habitats, depending whether they are juveniles or adults, sampling must occur at each juvenile or adult habitat. The age structure of juvenile goliaths in mangroves has been well studied. You are not going to find juveniles in spawning aggregations, because only individuals who are no longer juveniles and have working gonads (ovaries and testis) will show up at a spawning aggregation in the adult habitat. Scientists are now studying the age structure of adult goliaths using non-lethal techniques as published here: http://www.int-res.com/articles/esr2009/7/n007p213.pdf


Sampling spawning aggregations is the most cost effective and scientifically accurate way to obtain the age structure of adults in this case. This sampling strategy has been established by the Society for the Conservation of Reef Fish Aggregations (SCRFA), as well as by the Grouper and Wrasse Specialist group, a think-tank of experts that counsel the International Union for the Conservation of Nature (IUCN). Due to cost-effectiveness and scientific accuracy, sampling spawning aggregations has been adopted by fisheries agencies in the United States and throughout the world.


Sarah Frias-Torres, Ph.D. Independent Scientist
(305) 479-0312
Twitter: @GrouperDocBlog: Grouper LunaAcademia:Academia.edu | Sarah Frias-Torres

 

[aue-mike]

Sarah Frias-Torres	3:08 PM (3 hours ago)		​

In addition, goliath groupers form spawning aggregations where the entire breeding population in the state of Florida is concentrated in just a few locations.

This is not exactly accurate. The entire breeding population is not concentrated in just a few locations. While the established and expanding spawning aggregations do concentrate a significant number of animals in a given location, it is by no means the entire population. For whatever reason, individual and multiple (sometimes 30-40+ on a single site) adult goliath grouper generally maintain site fidelity during spawning season in most of Florida's waters. If you visit the ledges, shipwrecks, and artificial reefs along the Florida west coast during August and September, for example, you will still find your resident goliaths. Aside from the one well-known aggregation in Southwest Florida and a couple other lesser known sites, you generally don't find massive spawning aggregations in the Gulf. This could be a function of available habitat, as the West Florida Shelf covers so much area that there could be considerable distance for the animals to travel to form/establish an agg (in contrast to the compressed Southeast Florida Shelf). Who knows though....

Cheers,
Mike

 

[guyharrisonphoto]

I don't think Sarah was referring to studying the entire breeding population, but only the best way of getting the largest and best possible sampling of the adult fish population. For that, it makes sense to go where the most adult groupers are located and easliy accessible. The spawning aggregations are perfect for this. Knowing Sarah, if you clue her in on a great aggregation off the West Coast she will happily sample there as well.

It makes sense to proceed this way, when you have ready access to 30-50 adults as possible samples on almost every dive and at several different concentrated locations, as opposed to sampling at other times when they are spread out and you only find relatively few fish.

 

[aue-mike]

That's not what she said (re: studying breeding population) - she said "goliath groupers form spawning aggregations where the entire breeding population in the state of Florida is concentrated in just a few locations."

 

[dumpsterDiver]

Yes saying that ALL that all the sexually mature fish are concentrated in a FEW locations is ridiculous. If it were true, it would be very simple to count them... just make a count at a few sites and you have the population quantified.

 

[guyharrisonphoto]

That's not what she said (re: studying breeding population) - she said "goliath groupers form spawning aggregations where the entire breeding population in the state of Florida is concentrated in just a few locations."

Actually, you are nitpicking some words and ignoring others: "Sampling spawning aggregations is the most cost effective and scientifically accurate way to obtain the age structure of adults in this case." Read the full context. It is clear. She is talking about the sampling process and the best way to conduct the sampling. She mentioned the aggregations because that is where the greatest concentration of adult fish can be found. Maybe her phrasing was off on the "entire breeding" population because that was not the focus of either the question or her response. Besides, how do you know that the entire breeding population is not at the aggregations? Maybe there are some, even many, adult fish that do not breed every year, and they stay in their "resident" locations. And, possibly, breeding takes place outside of the aggregations. But, who knows? There is so much we do not yet understand about this species (still having to study basics like how long they live).

When scientists try to communicate with us here on the board, I think we should try to appreciate and understand the information they are trying to provide. Legitimate criticism is certainly part of the process, but jumping on an out of context phrase, and then calling her post "ridiculous" or making it seem like she is giving misleading information, are not well taken and are one of the reasons it is so difficult to start an intelligent internet conversation about almost anything.

 

[Reef_Haven]

I'll make a prediction.
80% are 6 - 10 years, 15% are 10 - 14, 4% are 15 - 24, and <1% are over 24.

Unfortunately there is no historical data before 1992, a time when this fish was in severe decline. At that time ~10% were over 24. How do we know that the historical population didn't consist of 25% or more > 24 years?