S .S. Montgomery J. Exp. Mar. Biol. Ecol. 255 2000 175 –186
181 Table 1
Analyses of numbers of i recruits, ii pueruli and iii juvenile stages of J . verreauxi on collectors between
a
type of Location exposed or sheltered to sea-swell and Position of collectors with respect to reef Source of
df Recruits
Pueruli Juveniles stages
variation MS
P MS
P MS
P C 5 0.23 ns
C 5 0.26 ns C 5 0.31 ns
Exposure, E 1
0.04 ns
0.01 ns
0.01 ns
Sites, SE 2
0.02 ,ns
0.01 ,ns
0.001 ns
Position, P 1
0.10 ns,
0.05 ns,
0.01 ns
E3P 1
0.01 ns
0.01 ns
0.0001 ns
P3SE 2
0.01 ns,E
0.004 ns,E
0.003 ns
Residual 29
0.01 0.01
0.00 Total
55
a
The degrees of freedom for the residual have been adjusted for missing replicates. Higher-order effects have been pooled P . 0.25. ns, non-significant P . 0.05; significant P , 0.05; significant P , 0.01,
ns,E, term was non-significant in original model but pooled with residual; ,ns, term was significant in original model but non-significant after pooling procedures; ns,, term was non-significant in original model but
significant after pooling procedures. Cochran’s test, C.
collectors at sea on 1 day 300 min. It cost 40 min to do each site. This was determined by measuring the time it took to prepare and travel to each site during this sampling.
Similarly, I determined that it cost 10 min to sample each collector.
3. Results
A total of 512 recruits of J . verreauxi were caught during the experiment. Mean
catch-rates of recruits from collectors set at the Position far from reef were greater than those from collectors at the Position near reef Tables 1 and 2, Fig. 3. When data were
analysed separately for pueruli and for the sum of first instar and early stage juveniles referred to below as ‘juvenile stages’, there were differences in the spatial patterns
between these two categories of development. Catch-rates of pueruli were greater on collectors set at the Position far from reef, whereas there were no significant differences
in catch-rates of juvenile stages between Positions.
Lengths of pueruli ranged between 9 and 11 mm CL, whilst those of juvenile stages were between 9 and 19 mm CL Fig. 4. Most individuals within the juvenile stages
Table 2
a
SNK comparisons of mean numbers S.E. for Position P 5 0.05 Near
Far Recruits
0.08 0.01 ,
0.16 0.01 Pueruli
0.04 0.01 ,
0.09 0.02
a
‘5’ indicates not significant, ‘.’ indicates greater than and ‘,’ indicates less than.
182 S
.S. Montgomery J. Exp. Mar. Biol. Ecol. 255 2000 175 –186
Fig. 3. Mean catch-rates 1S.E. of J . verreauxi recruits sampled from collectors at locations exposed E or
sheltered S from sea-swell and at Positions Near or Far 200 m from reef.
category were shorter than 13 mm CL and those longer than 15 mm CL occurred only on collectors at the Position near reef.
3.1. Cost–benefit analyses The variance among sites and collectors and the derived optimal number of collectors
and sites to be sampled are shown in Table 3. Having determined the appropriate numbers of replicate sites and collectors, the standard error of the mean of the data for
one sample period may be estimated as the square root of the variance calculated in Eq. 3.1. Results suggested that, for one location, it was optimal to sample three collectors
at each of three sites. This provided an estimate of mean relative abundance with a standard error of around 20 of the mean, for one sampling time at one location.
4. Discussion
