Conch, Lobster and Sea Cucumber

Regular monitoring of Queen conch, Caribbean spiny lobster and ‘Donkey Dung’ sea cucumber is carried out collectively under the Commercial Benthic Species monitoring program. Due to indications of possible overharvesting in recent years in PHMR, the on-going monitoring aims to determine stock levels of commercial benthic species and inform sustainable catch quotas.

Results are compared with two types of surveys; landings (“fisheries dependent”) surveys and underwater visual (“fisheries independent”) surveys to measure mean size, gender, population structure, population density of the three species, as well as comparing differences between management zones in the reserve (Replenishment Zones vs General Use Zones). 

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Lobster and Conch:

Lobster and conch are monitored at the start and end of their respective closed seasons. Conch is measured using shell length and lip thickness and lobster are measured using carapace length. Analysis of population structure using size frequency distribution enables us to monitor stock maturity over time; extremely important for predicting future productivity of the fishery and thus setting sustainable catch limits.

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Current results have found a size increase in lobster and conch but a decrease in overall abundance in both Replenishment Zones and General Use Zone. A major decline was observed in adult conch and lobster in the summer of 2011 and may have been caused by poor water quality in the benthic zone (hypoxia or low levels of dissolved oxygen) due to the growth and subsequent death of a regional scale algal bloom. The initial decline may have resulted in reduced reproduction in 2011 leading to a reduced spawning population in 2013. The conch population could therefore become even lower in the next 2-3 years causing a decline in the population between 2015-16.  While Managed Access is resulting in improved management of conch in PHMR, close monitoring and conservative management is still necessary to overcome the legacy of pre-Managed Access fishing pressure combined with natural phenomena such as the algal bloom. 

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Sea cucumber:

Sea cucumber monitoring was carried out in a variety of different habitats and the population was found to have decreased in all zones in 2012 and 2013.  This is thought to be due to overharvesting in the first year of licensed extraction of this new fishery product and is likely to result in poor catches in the future, as has been documented in multiple other fisheries such as in Panama and Venezuela. A larger sample size is now necessary to increase confidence in these observations.

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Future:

Results have shown the need for smaller length-based size restrictions. But it is important to note that recruitment of lobster has been shown to be better in Replenishment Zones (RZs) showing that RZs are an effective tool for allowing stocks to regenerate, but that they are not currently large enough to provide sufficient spill over to replenish General Use areas.

Continued monitoring is recommended as well as a revision of the size limits for conch and integration of conch lip thickness into size limit legislation to ensure only sexually mature adults are harvested.  It is thought a moratorium is needed in the short term for sea cucumber and finally it is recommended that 20-30% of the PHMR should become a Replenishment Zone to achieve sufficient stock replenishment of commercial species in General Use areas.

 

 

Date: November 14, 2014 Author: clarebaranowski
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