Caldow, C.

Clark, R.

Folger Renchen, G.

Olsen, D.

Pittman, S.

Aquatic Commons

 Proceedings of the 63rd Gulf and Caribbean Fisheries Institute     November 1 - 5, 2010   San Juan, Puerto Rico 
 
Assessing the Ecological and Economic Impact of Derelict Fish Traps in the U.S. Virgin Islands 
 
KEY WORDS: Derelict gear, ghostfishing, fish traps, marine debris, fisheries 
 
GABRIELLE FOLGER RENCHEN1*, SIMON PITTMAN2, RANDY CLARK2, CHRIS CALDOW2, and DAVID OLSEN 
1University of the Virgin Islands, NOAA Biogeography Branch UVI, Box 384 #2 John Brewers Bay,  
St. Thomas, VI 00802 U.S. Virgin Islands,  *gabby.folger@gmail.com.    
2NOAA Biogeography Branch, 1305 East-West Highway 9th Floor N/SCI-1, Silver Springs Maryland 20910 USA. 
 
 
Evaluar el Impacto Ecológico y Económico de Capturas de  
Peces Abandonados en las Islas Vírgenes  
 
PALABRAS CLAVE:  Capturas de peces abandonados, impacto ecolólogico, pesquerías, Islas Vírgenes 
 
 
Évaluation de L'impact Économique et Écologique de Pièges à  
Poissons Abandonnées dans les Iles Vierges 
 
MOTS CLÉS:  Pièges à poisons abandonnées, l’impact écologique, Iles Vierges 
 
EXTENDED ABSTRACT 
Fish traps are a widely used multi-species fishing gear in the Caribbean and around the world. Like most marine 
industries, the trap fishery can result in marine debris through intentional disposal of unwanted traps at sea, loss of traps 
through storms and strong surge or currents, lines cut by boats and ships and through abandonment.  Derelict fish traps are 
often considered a threat to the marine environment due to “ghostfishing” and habitat damage.  Ghostfishing is a process 
that occurs when a fisherman has lost all control over the fishing gear and it continues to fish and induce mortality. Impact 
to marine habitats is thought to occur from the physical disturbance to coral and other biota when traps are mobilized by 
storms, sea swell and strong currents.  Around the world, derelict fishing gear has become a great concern to the fishing 
industry and other marine stakeholders, as well as management agencies and the broader public sometimes leading to 
marine debris removal programs.  In the Caribbean region, very little is known about the distribution of derelict traps and 
whether they pose a threat to fisheries livelihoods and to marine species and habitats.  Threat assessment is required to 
determine if modifications to fishing practices are required and to provide reliable information to decision makers in 
resource management to determine the level of risk to the environment and if actions such as trap removal or trap disposal 
programs are required.  Due to the large gap in knowledge about derelict fish traps in the U.S. Virgin Islands, the objectives 
of this study were to first determine the scale and distribution of derelict fish traps and then experimentally examine their  
ecological interactions through the use of experimentally controlled and monitored derelict fish traps.  It was estimated that 
~4,800 fish and 3,100 lobster traps are fished in the areas surrounding St. Thomas and St. John.  To determine the spatial 
distribution of trap fishing effort and the known locations of lost traps in the USVI, we first developed a participatory 
mapping approach in partnership with the St. Thomas Fisherman’s Association (STFA).   Trap fishermen provided locations 
of fishing effort on a map of the shelf areas around St. Thomas and St. John that was divided up into 1 km  x 1 km grid 
cells.  Fishermen provided geographical coordinates for the locations were they had lost traps in the past. This information 
was used to:  
i) Guide the sampling design for a controlled field experiment to assess the ecological and economic impacts of 
derelict traps; and  
ii) To support a pilot study using autonomous underwater vehicles (AUV’s) to detect derelict fish and lobster traps. 
 
The research reported here focuses on the use of controlled experiments to examine derelict fish traps. The overall 
objective was to provide reliable quantitative scientific information to the fishing community and resource managers on the 
impact of derelict fish traps in the U.S. Virgin Islands.  This experimental evidence is intended to help decision makers 
evaluate the threat from derelict traps and determine if derelict traps should stay in-situ or be removed.  Specific questions 
investigated in this study included determining the amount of ghostfishing and mortality that occurs in fish species caught 
in experimental derelict traps, and how they behave including residence time, physical condition, time of capture and 
Page 42  63rd Gulf and Caribbean Fisheries Institute  
 
activity in the traps.  Possibly affecting residence time for 
specific species, biodegradable rot cord deterioration rates 
were monitored to determine the amount of time needed for 
the escape panels to open.  Trap movement was also 
incorporated as a question so that distance and habitat 
damage could be quantified if it did occur.  
In order to determine the impact of ghostfishing, 
unbaited fish traps were deployed at inshore and offshore 
locations in St. Thomas, USVI where derelict fish traps are 
currently present.  Six of the experimental traps were 
actively fishing and six were left with the escape panels 
open.  The traps were surveyed three days a week for six 
months for species abundance, size and mortality.  General 
behavioral observations were also recorded such as 
aggression, avoidance, attempting to escape etc.  Biode-
gradable rot cord deterioration was documented through 
photographs and the number of days before the rot cord 
snapped and the escape door opened were recorded.  
Economic loss was determined by calculating the length-
weight relationship for each species mortality and current 
market prices.  To assess fish behavior in the traps, a 
“TrapCam” was deployed for continuous twenty-four hour 
periods.   Fish entry and exit times were documented and 
behavior such as species interactions and activity periods 
were recorded.  
Five percent of the fish species caught in the experi-
mental derelict fish traps experienced mortality. Mortality 
was comprised of eleven species, with porgies (Calamus 
calamus) exhibiting the highest mortality; thirteen percent 
of all porgies captured perished, comprising 30% of the 
overall mortality.  The economic loss was estimated at 
approximately $160. The biodegradable rot cord took an 
average time of approximately four months to snap and an 
average of approximately 1.5 months later for the escape 
panel to open.  This estimate was based on previously un-
used traps and rot cord; with normal trap usage the 
biodegradable rot cord is likely to snap sooner and 
therefore the deterioration times are considered a worst 
case scenario, yet have revealed the potential problems 
with trap panels opening after cord has snapped. Once in 
the traps most species exhibited behaviors such as banging 
into the sides of the traps and swimming frantically, all of 
which are not typical behaviors of un-trapped fish.  
Snapper species tended to avoid individuals of other 
species of fish, while trunkfish spent a higher proportion of 
time trying to escape through the trap mesh. Angelfish 
tended to swim frantically and act aggressively towards 
other species. 
Assessing the impacts of experimental derelict traps 
demonstrated that derelict fish traps can cause mortality, 
although 95% of fish were able to eventually escape 
through the trap the way they had entered.  Sub-lethal 
physical damage was observed, but post-escape survival 
rates are unknown. Although lower than expected mortality 
was recorded, ghostfishing does occur and can lead to 
mortality.  Modifications to fishing practices and gear 
design could minimize both the abundance of derelict traps 
in the marine environment and the impact of derelict traps.  
 
 
 
 
 
 
 
 


Assessing the ecological and economic impact of derelict fish traps in the U.S. Virgin Islands. [Extended abstract]

http://aquaticcommons.org/15506/1/GCFI_63-7.pdf

Assessing the ecological and economic impact of derelict fish traps in the U.S. Virgin Islands. [Extended abstract]

Abstract

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