| dc.description |
Three low -relief banks (Heald Bank , Sabine Bank , Freeport Rocks ) in the
northwestern Gulf of Mexico were evaluated as lane snapper (Lutjanus synagris
Linnaeus , 1758 ) nursery habitat . Trawl surveys were conducted in three habitat types
(inshore mud , shell ridge , offshore mud ) , designated by side -scan sonar surveys , to
determine patterns of distribution and abundance . Heald Bank and Sabine Bank were
trawled in 2003 while Freeport Rocks was trawled in 2000 (Freeport A ) and 2004
(Freeport B ) . Density of lane snapper was higher on Sabine Bank (20 .8 ± 2 .8 ind ha -1 )
than on Heald Bank (1 .1 ± 0 .4 ind ha -1 ) , Freeport A (12 .7 ± 2 .3 ind ha -1 ) or Freeport B
(3 .0 ± 1 .0 ind ha -1 ) . Habitat -specific differences in density were observed , although
patterns were not consistent among banks . Highest densities of lane snapper were found
on Heald Bank’s offshore habitat (1 .7 ± 1 .0 ind ha -1 ) , Sabine Bank’s ridge habitat (26 .5
± 6 .9 ind ha -1 ) , and on the inshore habitat of Freeport A and B (17 .6 ± 4 .9 ind ha -1 and
4 .8 ± 3 .6 , respectively ) . Otolith microstructure analysis was performed on lane snapper
collected in trawl surveys to determine age , hatch -date distribution , growth and mortality
of new recruits . Hatch dates ranged from May 1 to August 31 , peaking in June for
Freeport (A and B ) and in July for Heald Bank and Sabine Bank . Growth rates varied from 0 .90 mm d -1 at Heald Bank to 1 .27 mm d -1 at Sabine Bank , and rates were highest
on the ridge habitat of Sabine Bank (1 .31 mm d -1 ) . Mortality of post -settlement lane
snapper was higher on Sabine Bank (15 .2 % d -1 ; Z = 0 .165 ) , than on Freeport A (9 .2 % d -
1 ; Z = 0 .097 ) , and was greatest on the ridge habitat of Sabine Bank (24 % d -1 ; Z = 0 .275 ) .
Recruitment potential (G : Z ) , evaluated on habitats at Sabine Bank , was highest on the
offshore habitat , with a value greater than 1 .0 , indicating higher potential contribution to
the adult population . Results indicate Heald Bank , Sabine Bank , and Freeport Rocks all
serve as settlement habitat of lane snapper , which appear to be capable of successful
settlement across a variety of habitats and banks . |
|