Searching for SpawnersLatest update November 28, 2018 Started on September 1, 2018
Once a year, some species of fish (groupers and snappers) gather together in huge clouds to spawn. These spawning aggregations are miraculous to observe. They are also easy to fish and fish hard if you know when and where to find them, so they are smaller these days. We are studying spawning aggregations in Belize and looking to see if we can find some unknown ones. Stay tuned as we go deep in search of one of the most spectacular strategies that fish have evolved to maximize reproductive success – spawning aggregations!
The conservation status of the Nassau grouper (Epinephelus striatus) has now been revised to CRITICALLY ENDANGERED across the Caribbean region based on the latest International Union for the Conservation of Nature (IUCN) assessment (Sadovy et al. 2018) published last week (https://www.iucnredlist.org/species/7862/46909843).
This new assessment indicates that Nassau grouper populations, including spawning aggregations, have declined by more 80% over three generations (1980-2018), for fish which live approximately 16 years. Overfishing is considered the major threat to this species, particularly heavy fishing on spawning aggregations (SPAGS), however, loss of quality coral reef habitat is also a factor.
At least 15 spawning aggregation sites are known from Belize, of which 13 are protected by law. However, recent data indicates that only a few hundred to a few thousand fish remain at each site (Burns Perez and Tewfik 2016, Proceedings of the Gulf & Caribbean Fisheries Institute). All these aggregation sites have undergone dramatic declines in fish abundance over the past two decades.
It is critical to maintain consistent monitoring and enforcement on SPAG sites in order to prevent the extinction of this iconic Caribbean species, Nassau grouper, along with other groupers and snappers. We will be deploying our OpenROV soon to add to our ongoing monitoring and conservation efforts of aggregating fish species at Glover’s Atoll and throughout Belize.
Many fish species form dramatic groupings when they reproduce. These "Spawning Aggregations" – called "SPAGs" by scientists - are critical for many fish. They allow individuals to select mates, synchronize spawning, and optimize the likelihood of survival of their offspring. Unfortunately for the fish, these seasonal SPAGs also allow fishers an easy way to catch a lot of fish in a short time. In Belize, fishing SPAGs, most notably groups of the endangered (and delicious) Nassau grouper, started as far back as the 1920s. Hard, frequent fishing has decreased the number of fish seen year after year. This is leading to fewer fish, smaller fish, skewed numbers of male and female fish, and, overall, lower reproduction. It may lead to the crash of these fish populations. The Northeast Point spawning site at Glover’s Atoll, home of WCS’s research station, has been monitored each season by WCS and Belize's Fisheries Department since 2001. We count fish during short (15 min) and deep (> 30 m) SCUBA dives. Since 2016, individual groupers have been measured using GoPro cameras with paired lasers. We will now use ROVs to the project and see if they can be used to conduct the counts and add underwater time to the surveying at the NE point as well as at a rediscovered SPAG site for Tiger grouper. We also are hoping to find new, unknown SPAG sites at Glover’s Atoll.
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