Sawdust in the Water? Trichodesmium Algal Blooms

 Boaters and beachgoers in southwest Florida periodically observe what appears to be large mats of

“sawdust” floating on the water’s surface. What they are seeing is not the remnants of someone’s woodworking project, but a marine cyanobacteria (also known as blue green algae) called Trichodesmium.

Trichodesmium naturally occurs in tropical and subtropical waters including the Gulf of Mexico. When environmental conditions are right, Trichodesmium cells rapidly repro-duce resulting in a bloom of the cyanobacteria that can be visible by onlookers.

According to the Florida Fish and Wildlife Research Institute, Trichodesmium cells form long chains, called trichomes. Trichomes then can gather into colonies called “puffs” or “tuffs,” and these colonies can aggregate at the surface of the water and form large mats that can extend for miles (also called “sailor’s sawdust”). The amount of Trichodesmium on the surface may vary with time of day, as this species is capable of migrating up and down in the water column. Blooms generally occur offshore in nutrient-poor waters, but currents and winds can push them near shore.

Trichodesmium blooms can take on a range of colors depending on stage of the bloom. Healthy blooms are typically brown in color, while blooms in initial decay may take on a green appearance due to accessory pigments leaching out and exposing the cyanobacteria’s chlorophyll. When the chlorophyll begins to deteriorate the blooms appear white in col-or. Trichodesmium blooms are also reported to have a unique “sweet” smell when it decays and large blooms can turn the water red or pink when stressed cells leaks out water soluble, accessory pigments.

Unlike other algal blooms that occur in the region, Trichodesmium blooms are not related to coastal nutrient sources or pollution. Most or all of the nutrients Trichodesmium requires are taken up directly from the water.

Interestingly, the occurrence of Trichodesmium blooms in Florida is thought to be connected to weather events on the other side of the planet. Blooms in the Gulf of Mexico tend to occur between May and September, which is also a time of high storm activity in the Sahara Desert in Africa. Iron-rich dust from these storms are transported across the Atlantic Ocean by wind currents, and deposited into the Gulf of Mexico. Trichodesmium cells contains enzymes that utilize this high concentration of deposited iron to convert nitrogen into useable forms.

While Trichodesmium blooms can be aesthetically unappealing, it is not toxic and does not pose a health risk to humans. Ironically, Trichodesmium blooms are often seen prior to a Florida red tide bloom, which is a toxic algae that can result in numerous fish kills and human health issues.

 
Reference: http://myfwc.com/research/redtide/archive/historical-events/trichodesmium-fl-2004/

2013 Florida Seafood Brown Bag Webinar Series

Join the Florida Sea Grant Extension Programs from Collier and Miami-Dade Counties for the 2013 Florida Seafood Brown Bag Webinar Series. This year's sessions will focus on seafood health and saftety.
See below for dates and topics.
To register for this FREE program visit: http://2013seafoodsafetyseries.eventbrite.com/#

Are You Smarter than a Stone Crab? January 23rd

It’s that time again for another round of “Are You Smarter than A Stone Crab? The next tour will be Jan 23, 2013. This time the tour will begin at the Evergaldes City Museum so participants can learn more about the heritge associated with commercial fishing in Everglades City. This program is a great way to learn more about the economic and cultural importance of one of Florida’s most valuable fisheries. Hope to see you there! To register, click on the flyer below.

 

2013 SW Florida Marine Fisheries Workshop

I hope you will be able to join us for our 2013 SW Florida Fisheries Regulations and Management Workshop!

 

To register visit:

http://2013fisheriesworkshop.eventbrite.com/

A Florida Stone Crab's Life Cycle

Stone crabs are one of Florida’s most valuable fisheries, and like other species we depend on for seafood, they often utilize a variety of habitats and undergo a series of physical transformations throughout their life.

Mating in stone crabs takes place near and offshore during the fall and can only occur when the female has molted and her shell is soft. While eggs are fertilized internally, they are eventually deposited beneath the female’s abdomen or “apron” in an external mass called a sponge. Spawning typically occurs during summer months and females can release millions of fertilized eggs in several intervals.

The eggs, which float in the water column, usually hatch within two weeks and then larval development takes approximately a month to complete. Larvae are planktonic and are transported to coastal and estuarine waters. The first larval stage to emerge from the egg is a called a zoea. As the zoea larvae grows they pass through five distinct changes before developing into a post-larval form called a megalopae. The megalopae, which is more crab-like in appearance, will settle to the bottom where it will take shelter. Here, it will molt several times before transitioning to a juvenile stone crab.

A juvenile stone crab in my hand

Unlike adult Florida stone crabs, which are tan in color, juvenile stone crabs up to about 2.5 cm (1 inch) in width are deep purple to black with white flecks on their carapace. Like the adults though, they have distinctive white bands on their legs. As they grow and molt, they will begin to take on the appearance of adult stone crabs. Juveniles can be found living among shell rubble, oyster beds, sponges, and tunicates in estuarine and nearshore habitats.

An adult stone crab hiding under a ledge

Florida stone crabs becomes sexually mature by two years of age. Adults will move around and can be found living in burrows among seagrass communities, or offshore out to depths of 200 feet, where they live under ledges or in burrows and crevices associated with hardbottom communities. Age estimates suggest male Florida stone crabs live for seven or eight years while females can live up to eight or nine years.

 

Overview of Florida's Commercial Snapper Fisheries

Image credits: Dianne Pebbles, SAFMC

Snappers (Family Lutjanidae) are a widely-distributed group of fishes that inhabit a diverse range of coastal and marine habitats. They are generalized predators characterized by the presence of strong jaws with prominent canine teeth. Generally smaller than grouper, they can range from a few pounds to over 60 pounds. Florida has approximately 15 snapper species; only half of which are targeted by commercial fishermen as they are prized for their firm texture and mild flavored meat.

 

Landings

2010 Florida Snapper Landings (lbs)
by FloridaCoast: Source:FWRI

Over the last decade, an average of 4.3 million pounds of snapper worth an average of $10.7 million were landed by Florida commercial fishermen. Despite the diversity of snappers found in Florida waters, approximately 90% of commercial landings come from three primary species; yellowtail, vermillion, and red snapper. Top landings for red and vermillion snapper occur in the Panhandle region, while south Florida dominates yellowtail landings. Much like grouper, the overwhelming majority of snapper are landed on Florida's Gulf coast in federal waters.

Management
Snappers are heavily regulated with high demand from both the commercial and recreational sectors. Stocks are managed separately in the Gulf and Atlantic waters. State regulations typically mirror federal rules for consistency, but this is not always true. Management of the snapper fishery has been challenging due to a lack of data on both the resource and the fishery. Improved data collection during the 1980s and 1990s has provided more management information on some of the more commercially and recreationally valuable species, but lack of basic management data on many of the species still remains the major obstacle to successful management.

Status of Populations
Of Florida's three major commercial snapper species, yellowtail populations appear to be the most robust. They are neither overfished nor experiencing overfishing in either the Atlantic or Gulf of Mexico. While vermilion snapper are abundant in the Gulf of Mexico, population levels are lower in the Caribbean and South Atlantic. They are not considered overfished, but are experiencing overfishing in this region; management measures are currently in place to end overfishing.

* denotes the stock is undergoing a rebuilding plan.
Source: Gulf and S. Atlantic Fishery Management Councils

Perhaps no other snapper species has generated as much controversy surrounding its management than red snapper. Because of its high demand by both commercial and recreational fishermen, it has undergone intense fishing pressure for years and is one of the most tightly regulated fisheries in the United States. South Atlantic stocks of red snapper are overfished and experiencing overfishing. The decline in the Atlantic population is thought to have occurred since the 1950s with continued pressure in following decades. The 2008 stock assessment indicated that overfishing was occurring at 14 times the sustainable level. Based on this information, the entire snapper fishery was shut down in the beginning of 2010. Recent considerations to shut down large areas off of Florida and Georgia’s coasts to all snapper and grouper fishing was negated due to updated stock assessment data that indicated the stock was in slightly better shape than previously thought. It is expected, however, that the fishery will remain closed for several more years and a full recovery won’t be for several decades.



Source: NMFS

Since implementing a catch share program in 2007 the commercial Gulf red snapper fishery has seen a 40 percent increase in the total allowable catch. In fact, overfishing of red snapper in the Gulf ended in 2009. While still classified as overfished, the stock appears to be rebuilding faster than anticipated; even with the better than expected news, the stock is not expected to be fully recovered until 2032.

Several factors have contributed to the complexity associated with red snapper management:

Shrimp Trawl Bycatch
Historically, the unintended bycatch of juvenile red snapper in shrimp trawls contributed to a significant portion of snapper mortality. Over the past several years though, the domestic shrimp fleet has been significantly reduced due to fuel prices, competition with imports, and hurricanes. As a result, juvenile mortality levels have decreased, contributing to faster than expected rebuilding efforts. In addition, improved designs in Bycatch Reduction Devices (BRDs) in shrimp nets is thought to have contributed to recovery efforts.
Discard Mortality
Because of strict regulations such as closed seasons and size and bag limits, many red snapper are released by fishermen. Unfortunately, a significant percentage of these released fish (approximately 40% of released recreational fish and up to 90% of released commercial fish) do not survive, which further hinders management efforts to rebuild the fishery. Recent regulations requiring the use of circle hooks, dehooking devices, and venting tool have helped to reduce release mortality of released fish.
Management Mandates
In 2006 the Magnuson-Stevens Conservation and Management Act set new guidelines to end overfishing and rebuild U.S. fish stocks. The re-authorization directed managers to act quickly to implement regulations to reduce mortality and end overfishing of affected stocks. As a result, managers were forced to implement more stern actions to rebuild red snapper stocks. Public Perception
Despite red snapper populations being considered overfished, many fishermen report catching more than ever before. Part of the issue has to do with the life history of red snapper. Red snapper are thought to live at least 50 years, and larger fish do not always mean older fish. Despite recent increases in overall numbers of red snapper, the age structure of the population remains truncated and there are not enough older fish to successfully repopulate the stock. Adding to the frustration of fishermen is that the ongoing snapper regulations have occurred during tough economic times, thus affecting their ability to earn a living from snapper fishing.

References:

• Fishwatch. U.S. Seafood Facts: http://www.nmfs.noaa.gov/fishwatch/
• Florida Fish and Wildlife Research Institute:
• http://myfwc.com/research/saltwater/fishstats/commercial-fisheries/landings-in-florida/
• Gulf of Mexico Fishery Management Council: http://www.gulfcouncil.org/
• Louisiana Sea Grant: http://www.lsu.edu/seagrantfish/faqs/index.html
• South Atlantic Fishery Management Council: http://www.safmc.net/
• South Carolina Aquarium's Sustainable Seafood Initiative:
• http://scaquarium.org/SSI/PDFS/newsletters/2011_Issue1.pdf

Recording: Florida Hard Clam Industry Webinar

Did you know that Florida is one of the top producers of farm raised hard clams in the country?
I invite you to watch a recording of a webinar I presented on Florida's hard clam aquaculture industry. There are three main goals of the webinar

1. Increase your knowledge of basic hard clam biology & ecology
2. Enhance your understanding of the trends, importance, & management of Florida’s hard clam industry
3. Make you more informed about the purchasing, storing, & handling of hard clams

Webinar Recording

View the Blackboard Collaborate recording

Hard Clam webinar Evaluation

How did I do? If you watch the webinar please take a minute to complete a short evaluation. Your feedback will me in the preparation of future presentations

 https://www.surveymonkey.com/s/hardclam

Hard Clam Resources

I refer to several hard clam resources during the presenation and want to share them with you.

• UF/IFAS Florida Shellfish Aquaculture Resource: shellfish.ifas.ufl.edu

• FWC Hard Clams Sea Stats Publication: http://www.scribd.com/doc/44618794/Sea-Stats-Clams?in_collection=2498616

• “Fresh from Florida” Hard Clam Resources http://www.florida-agriculture.com/consumers/crops/seafoodproducts/species/clams/

Florida Seafood Brown Bag Webinar Series Recordings

 Finally, if you would like to watch the recordings of past webinars in our series visit:

http://miami-dade.ifas.ufl.edu/environment/sea_grant_seafood.shtml