106 
Fishery Bulletin 120(2) 
However, the mean of 0.4 for the ratio of L,, to L.., shown 
in Figure 3, cannot be used for the wool sponge to test the 
hypothesis in Pauly (1984) (see also Pauly, 2021a), which 
predicts values for this ratio in WBE. The reason is that 
the data in Storr (1964) do not pertain to the mean size at 
which wool sponges mature (i.e., the length at which 50% 
of a cohort reaches maturity) but do indicate the minimum 
size at which some of them do. 
Respiration 
The respiratory area of the wool sponge is not known. 
Measurements of the respiratory area for the European 
coastal sponge Suberites massa, taken decades ago, have 
been used to estimate the area at 100 cm”/g (Piitter, 1914; 
von Ledebur, 1939). Gatti et al. (2002) used oxygen micro- 
probes to measure oxygen concentrations within the tissue 
of the Mediterranean bacteriosponge Suberites domuncula 
and detected oxygen concentrations of approximately 50% 
of the surrounding ambient seawater. Weisz (2006) used 
oxygen microprobes and tetrazolium salts to examine oxy- 
gen concentrations and the occurrence of anoxic zones in 
4 species of low-microbial-abundance and high-microbial- 
abundance sponges. Oxygen concentrations within the 
ectoderm and endoderm of low-microbial-abundance 
sponges were similar to ambient seawater concentrations, 
whereas endoderm tissues in high-microbial-abundance 
sponges were all hypoxic or anoxic. 
The decline of the oxygen content 
in the interior of the near-spherical 
sponge Barrett’s horny sponge stud- 
ied by Hoffmann et al. (2005) can be 
re-expressed as follows: 
Fraction of ambient oxygen level = 
if Leg eee) (15) 
where r =the depth (in centimeters) 
within the sponge. 
The decline of oxygen level is most 
rapid at the inflexion point of 2.76 cm 
(95% CI: 2.52-2.98), and the slope at the 
inflexion point (S=-0.675) has a 95% CI 
of —0.998 to -0.548 (Fig. 4). The gen- 
erality of the numbers estimated with 
Equation 15 and illustrated in Figure 3 
cannot currently be assessed, given that 
they were derived from an experiment 
on one species at one (low) tempera- 
ture (6—-15°C) (Hoffmann et al., 2008). 
However, the shape of this relationship 
is likely realistic and could be adapted 
to different species by increasing or 
decreasing the 2 parameters of Equa- 
tion 15 (or Equation 10). The provided 
equations allow computing the oxygen 
level in near-spherical sponges by add- 
ing the dissolved oxygen in successive 
S 
oO 
ie) 
> 
x 
fo) 
a 
S 
2 
xe} 
€ 
oO 
= 
fo) 
< 
2 
= 
Q 
Oo 
_ 
us 
depth layers, and the oxygen level of each depth layer is 
the mean of the oxygen level at its outer and inner limits. 
Sponges in fisheries, ecosystems and ecosystem models 
Official estimates of fisheries catch of sponges are available 
from the FAO (available from website), originating from 
25-30 countries and territories and adding up to nearly 
40,000 metric tons (processed dry weight) from 1950 to 
2019. However, both the number of countries exploiting 
sponge populations and the level of their catches are likely 
underestimates, requiring correction as has been recently 
performed through catch reconstruction for the catch of 
the world’s marine fisheries (Pauly and Zeller, 2016a, 
2016b), even if done with the exclusion of sponges. 
Empirical estimates of effects of commercial fisheries on 
sponge communities are virtually unavailable, although 
in south Florida, management limitation of harvest based 
on the usé of artisanal techniques appears to have resulted 
in a sustainable fishery (Butler et al., 2017). More devasting 
to sponges in many areas are mass die offs of sponges due to 
disease, cyanobacteria blooms, and poor water quality that 
can extend over hundreds of square kilometers with strong 
effects on ecosystems (Butler et al., 1995; Herrnkind et al., 
1997; Webster, 2007; Gochfeld et al., 2012; Wall et al., 2012; 
Butler et al., 2018). 
In EcoBase, a database of Ecopath food-web models 
(Colléter et al., 2015; available from website) that included 
3 4 5 
Sponge depth (cm) 
Figure 4 
The decline of oxygen content inside an approximately spherical sponge, the 
Barrett’s horny sponge (Geodia barretti), based on specimens sampled at 
depths between 100 and 200 m on the hard-bottom slope of Korsfjord near 
Bergen, Norway. The values were read off figure 2 in Hoffmann et al. (2005) 
and re-expressed as a fraction of ambient oxygen levels. The relationship 
between oxygen content and sponge depth is fitted with a logistic curve, and 
the gray shaded area represents the 95% confidence interval. 
