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Fishery Bulletin 106(3) 
The most important cause for the loss of traps was 
interaction with other gears (41%), followed by bad 
weather (39%), and fouling on rough bottom (18%). 
Skippers also indicated that gear loss could be caused 
by other factors (2%), especially theft. The main rea- 
son for trap loss in the local fishery was interference 
with other gears (42.6%) and fouling on rough bottom 
(42.4%) in the Sotavento and Barlavento areas. In the 
case of the coastal fishery, the main reasons for trap 
loss were bad weather (40.4 %) in the Sotavento area 
and interference with other gears in the Barlavento 
area (40.0 %). 
Discussion 
In comparison to the octopus traps, fish traps caught a 
greater variety of species and the average catch per trap 
(in the period of days to weeks after deployment) was 
much greater. Groups of individuals of the same species 
of Sparidae were recorded in the same trap, often on 
subsequent monitoring dates, indicating that escape- 
ment rates were low or that individuals that died or 
escaped were replaced by conspecifics (Bullimore et al., 
2001). Abrasions on the head and snout from attempts 
to escape through the wire mesh also indicated that 
escapement rates were probably low (Bullimore et al., 
2001; Al-Masroori et al., 2004). There was a succes- 
sion in the capture of species; there were initially high 
catches of the target sea bream species, followed by the 
entry of larger predator-type species such as conger eel 
and fork beard. The predators were probably attracted by 
the smaller prey species within the trap, and the same 
individual predators were observed in the traps over 
weeks and in some cases for more than a month. 
There have been relatively few studies on fish escape- 
ment rates from traps, and comparisons have generally 
not been possible because of differences in trap design 
and size. Munro (1974) reported that escapement from 
Antillean fish traps used in the Caribbean averaged 
11.6% per day. Scarsbrook et al. (1988) reported a 0% 
escapement rate for sablefish ( Anoplopoma fimbria). Al- 
Masroori et al. (2004) assumed a 10% escapement rate 
from large, single opening wire traps in Oman, and a 
95% mortality rate for ghost-fishing traps. Given the 
design of the fish traps, our own observations of trapped 
fish, and the typical escapement rates reported in the 
literature, we believe that ghost fishing mortality rates 
of fish in the murejona traps are high and are caused 
by predation in the trap or are the result of injuries 
and starvation. On the other hand, we assume that 
octopus escapement rates were 100%. There may have 
been some trap-related mortality caused by predation 
because octopus require several minutes to exit a trap 
through the mesh and are therefore susceptible during 
that time to the attack of a moray eel or conger eel 
inside the trap. 
Catches in octopus traps decline sharply 24 hours 
after deployment, whereas fish trap catches peak one to 
two weeks after deployment, and long after the bait has 
been consumed or has deteriorated. Rapid consumption 
of bait has been supported by the findings of Castro et 
al. (2005), who reported that fish discards in this region 
are completely scavenged within 24 hours, and by the 
general knowledge that octopus fishermen must rebait 
their traps frequently. 
Optimal trap soak times of days or even weeks with 
asymptotic catch rates have been reported in a num- 
ber of studies (Munro, 1974; Mahon and Hunte, 2001; 
Al-Masroori et al., 2004). Typically, as seen with our 
fish traps, catches tend to decline and stabilize at low 
rates for long soak times. Munro (1974) reported that 
for long soak times, catch rates in Antillian fish traps 
stabilized at the point where daily escapement equaled 
daily ingress. 
Based on the relationship between rates of ingress, 
escapement, catch, and soak time, a variety of models 
have been used to model trap catches over time (Fogarty 
and Addison, 1997; Zhou and Shirley, 1997; Al-Masroori 
et al., 2004). The Zhou and Shirley (1997) is the only 
model where catches increase to a maximum of days or 
weeks after deployment and then decline, stabilizing at 
a low level. This model gave a good fit to the murejona 
data, where catches peaked two weeks after trap deploy- 
ment, and then stabilized at a mean of approximately 
one fish per trap. Octopus trap catches also stabilized 
at very low catches per trap, but were highest 24 hours 
after deployment. A simple exponential model (Al-Mas- 
roori et al., 2004) adequately describes the catches over 
time but does not model the low residual catches. Thus, 
we opted to use the Zhou and Shirley (1997) model for 
the octopus trap data as well. 
The results of the questionnaire survey showed that 
interaction with other gears (gear conflict) was the 
most important cause of trap loss. The large number 
of traps (often deployed without buoys at the surface 
to avoid theft) within a limited area where many other 
fishing vessels are operating simultaneously, coupled 
with long soak times, may explain these results. From 
our experience, fishermen who catch a longline of traps 
in their own gear often will simply cut the lines to dis- 
entangle the gears. Thus, the traps are often cut loose 
but fall close to where they had been fishing. The other 
major cause of trap loss was bad weather, often lead- 
ing to the loss of entire longlines of traps. This cause 
is particularly important for the larger coastal vessels, 
which tend to fish further from their homeports and in 
deeper waters. 
Given the fact that fishing with traps in the Algarve 
takes place in relatively shallow water, underwater sur- 
veys with divers are an appropriate method for monitor- 
ing catches in deliberately lost traps and for quantifying 
gear loss. Despite the problem of the loss of traps due 
to bad weather and interaction with commercial gear, 
it is possible to monitor both octopus and fish traps for 
prolonged periods. The use of divers permits the moni- 
toring of traps and their catches without disturbance. 
This method is vital for understanding trap catch dy- 
namics and the changes in catches after the bait used 
to attract fish and cephalopods is no longer present in 
