6 
Fishery Bulletin 116(1) 
they would also be more likely to escape predation (Wi- 
edemeyer, 1993). In the Salomon Islands, the growth 
rate, as well as the daily distance covered by the sand 
fish ( Holothuria scabra), was found to be related to 
substrate type, and the sandy areas were occupied only 
when individuals reached a specific size (Mercier et ah, 
2000). Inside the Ria Formosa, individuals of H. ar- 
guinensis move through a patchy environment; despite 
the relatively large percent coverage of Z. noltii (46% 
of the intertidal area) within the Ria Formosa, distri¬ 
bution of this seagrass species is highly fragmented, 
dominated by small patches from 0 to 5 ha (Guimaraes 
et al., 2012). These seagrass patches are separated 
by sand, mud, and marshes that sea cucumbers must 
pass through when searching for more suitable feed¬ 
ing areas, or probably for areas where they can avoid 
direct sunlight and desiccation (Gonzalez-Wangiiemert 
et al., 2013). However, the results obtained by Siegent- 
haler et al. (2015) in a small-scale capture-recapture 
experiment with H. arguinensis in the Ria Formosa, 
revealed that mean length was not a significant fac¬ 
tor in determining the distribution of this species, and 
its movement was independent of habitat type (sand 
and seagrass). In fact, movement of H. arguinensis was 
better explained by the need of specimens for shelter 
against UV-radiation, when individuals remain outside 
water during low tides (Siegenthaler et al., 2015). Fur¬ 
ther studies should be considered to evaluate whether 
the same pattern exists at larger spatial and tempo¬ 
ral scales than those considered by Siegenthaler et al. 
(2015), and also including a greater size range of ani¬ 
mals for the experiment. 
A faster growth rate could also be the result of a 
decrease in predation rate, mainly during the early life 
history stages. Although few predators are known to 
feed on sea cucumbers, several antipredation mecha¬ 
nisms has been described for holothurians (Francour, 
1997) and some of these mechanisms seems to be 
linked to animal size. For example, in the lolly fish, the 
strength of the toxin present on its skin significantly 
increases with the size of an individual (Castillo 2 ). 
On the other hand, the high growth rates of H. ar¬ 
guinensis in the Ria Formosa could be linked to the 
high productivity of this ecosystem, where a rich phy¬ 
tobenthos, of macrophytic and microphytic organisms 
(seagrass and diatoms) is located (Brito et al., 2009). In 
some mesoscosm experiments carried out on the Great 
Barrier Reef in Australia with lolly fish, it was found 
that higher food availability per individual increased 
growth rate (Lee et al., 2008). Therefore, further stud¬ 
ies of individuals from areas outside Ria Formosa, and 
with varying levels of natural productivity, should be 
carried out to confirm the growth rates we have re¬ 
ported here. 
2 Castillo, J. A. 2006. Predator defense mechanisms in shal¬ 
low water sea cucumbers (Holothuroidea). UCB Moorea 
Class: Biol. Geomorphol. Trop. Is]., Univ. Calif. Berkeley, 
Berkeley, CA. (Available from website.] 
The value obtained for the parameter C (Hoenig 
model) indicates a seasonal cycle of growth for H. ar¬ 
guinensis, which may cease at least during part of the 
year. According to Pauly (1987), Ts + 0.5 is the time of 
the year when growth is slower, and where Ts denotes 
the beginning of the sinusoidal growth oscillation. This 
winter point, suggests a reduction in the growth rate 
of H. arguinensis at 0.19 time units (the time unit for 
this study was a month, where a 0 time unit repre¬ 
sents the month in which the sampling started [No¬ 
vember 2012] and 1 time unit corresponds to the 12th 
month of sampling) from the beginning of the sampling 
year, which coincides with the months of January and 
February, when waters may have brackish conditions 
and the lowest temperatures occur in Ria Formosa 
(Newton and Mudge, 2003). Feeding experiments on 
H. arguinensis, in laboratory tanks, could confirm 
this reduction in growth rate during winter months 
because under rearing conditions, the species is sta¬ 
tionary and decreases feeding rate when water tem¬ 
perature is lower than 14°C (Domlnguez-Godino and 
Gonzalez-Wangiiemert 3 ). These low temperatures are 
common during winter months in Ria Formosa (Ramos 
et al., 2013). Another temperate sea cucumber species 
inhabiting the Aegean Sea, Holothuria tubulosa, ex¬ 
hibits similar behavior, with a negative specific growth 
rate at 15°C. At this temperature, individuals enter a 
hibernation phase and have a corresponding drop in 
metabolic rate, which directly affects their feeding ac¬ 
tivity (Giinay et al., 2015). 
This pattern of a complete shutdown in growth dur¬ 
ing winter is also found in other temperate species 
such as A. mollis (Morgan, 2012), C. frondosa (Hamel 
and Mercier, 1996), Parastichopus californicus (Palt- 
zat et al., 2008) and Holothuria theeli (Sonnenholzner, 
2003). Sea cucumbers, seem to have failed to adapt to 
large fluctuations in water temperature (Dong et al., 
2008), clearly showing an optimal temperature for 
growth which is close to the optimal temperature for 
food intake (Yang et al., 2005). Conversely, high wa¬ 
ter temperatures can also induce aestivation in some 
sea cucumber species, such as has been observed in 
Apostichopus japonicus and Australostichopus mollis 
(Yang et al., 2005). These results show that water tem¬ 
perature has an effect on the physiological performance 
of sea cucumbers and that their growth is largely in¬ 
fluenced by environmental conditions and food supply 
(Hamel and Mercier, 1996; Sonnenholzner, 2003). 
Acknowledgments 
This research was supported by the CUMFISH (PTDC/ 
MAR/119363/2010) and “Sea cucumber as new marine 
resource: potential for aquaculture” (CUMARSUR) 
(PTDC/MAR-BIO/5948/2014) projects funded by Funda- 
3 Donu'nguez-Godino, J., and M. Gonzalez-Wangiiemert. In 
review. Centro de Ciencias do Mar, Universidade do Al¬ 
garve, Campus de Gambelas, 8005-139 Faro, Portugal. 
