104 Fishery Bulletin 120(2) 
Table 2 
Estimates of food consumption (qg) and production (p) per unit biomass (6) and trophic lev- 
els from sources by the authors of 3 Ecopath food-web models in which a sponge group is 
explicitly included. These authors sampled sponges from 3 marine ecosystems: the Virgin 
Islands (Opitz, 1996), the central Great Barrier Reef in Australia (Tudman, 2001), and the 
Te Tapuwae o Rongokako Marine Reserve (TTMR) off the North Island of New Zealand 
(Pinkerton et al., 2008). See tables 3 and 5 and text in Pinkerton et al. (2008) for issues 
with the TTMR estimate, which appears to be the most credible of the 3 estimates of p/b 
in this table. 
Trophic qlb p/b 
Location level (year!) (year!) Source 
Virgin Islands, Caribbean 2.0 4.2 1.7 
Central Great Barrier Reef 2.0 3.0 0.9 
Opitz (1996) 
Tudman (2001) 
Pinkerton et al. (2008) 
TTMR, North Island, N.Z. 2.3 0.8 0.2 
an estimated 47,000 individual sponges of all types with 
a volume of approximately 17 m*/ha. On average, 10% 
of those sponges have diameters that exceed 25 cm, and 
wool sponges make up about 1% of the total sponge bio- 
mass (Butler et al., 2021). On coral reefs in the Carib- 
bean, over 500 species of sponges have been identified 
and their average percent cover of 16% (range: 2—75%) 
exceeds that of corals (Miloslavich et al., 2010; Loh and 
Pawlik, 2014). Clearly, sponges are a major component of 
many tropical marine ecosystems as are their ecological 
ramifications, and this importance is reflected in sponges 
being part of published ecosystem models. We examined 
this issue through the coverage of sponges in successive 
implementations of the commonly used 
Ecopath food-web modeling software 
(Christensen and Pauly, 1992; Colléter 
et al., 2015). 
Results 
Growth 
The parameters of the VBGF (Equation 4) 
from the diameter-at-age data in Table 1 
led to the following equation: 
Diameter (cm) 
D, = 31.5(1-e°1), (12) 
where D,=the predicted diameter at 
age ¢ in centimeters. 
The parameter t) (see Equation 4) is 
not included in this equation because it 
was set at zero, forcing the growth curve 
to start at the origin of the age scale 
in Figure 2. As for the value of 0.191 
year ' for the parameter K, its 95% CI, 
estimated by bootstrapping the data 
in Table 1, is 0.185-0.199 year’. This 
interval is likely to be an underestimate 
because the age-at-length data in Table 1 are means and 
therefore do not include variability in individual growth. 
However, even when available, data on individual growth 
variability are still difficult to consider when estimating 
VBGF parameters (Sainsbury, 1980; Wang and Thomas, 
1995). The estimate of asymptotic size is close to the max- 
imum size reported by Storr (1964), 12 in (or ~30.5 cm) 
up to the size at which the sponge’s spherical shape is 
maintained. 
Using Equation 3 to compute the relationship of diame- 
ter to volume indicated by the data in Table 1 leads to a 
mean value of parameter a of 0.55 for mediating between 
diameter in inches and volume in cubic inches. For the 
eSspom) — Hippospongia 
“Gy lachne 
Age (years) 
Figure 2 
Growth of the sheepswool sponge (Hippospongia lachne), also known as the 
wool sponge, in the upper Gulf of Mexico as indicated by a von Bertalanffy 
growth curve fitted to diameter-at-age data from Storr (1964) (see Table 1). 
The estimates of asymptotic length (i.e., diameter) and growth coefficient are 
31.5 cm and 0.191 year’, respectively. The horizontal dashed line indicates 
the asymptotic diameter (D.,). 
