EFFECTS OF SUBSTRATE SELECTION AND POSTSETTLEMENT SURVIVAL ON RECRUITMENT SUCCESS OF THE THALASSINIDEAN SHRIMP NEOTRYPAEA-CALIFORNIENSIS TOINTERTIDAL SHELL AND MUD HABITATS
Kl. Feldman et al., EFFECTS OF SUBSTRATE SELECTION AND POSTSETTLEMENT SURVIVAL ON RECRUITMENT SUCCESS OF THE THALASSINIDEAN SHRIMP NEOTRYPAEA-CALIFORNIENSIS TOINTERTIDAL SHELL AND MUD HABITATS, Marine ecology. Progress series, 150(1-3), 1997, pp. 121-136
We quantified recruitment of young-of-the-year (YOY) burrowing thalass
inidean shrimp Neotrypaea californiensis to 2 habitats of differing st
ructural complexity-epibenthic bivalve shell and bare mudflat-and exam
ined how differential settlement and post-settlement predation influen
ce patterns of YOY abundance. Local densities of shrimp were quantifie
d prior to construction of shell habitat in Grays Harbor estuary, Wash
ington (USA). Subsequent recruitment of YOY shrimp to epibenthic shell
and bare mudflat was measured during a peak settlement pulse and 10 m
o post-settlement. In addition, patches of sediment overlying shell wi
thin the shell plot ('subsurface shell') were sampled 10 mo post-settl
ement. Differential settlement in shell and mud habitats was quantifie
d in field and laboratory experiments. We also examined predator-prey
interactions between YOY Dungeness crabs Cancer magister and newly set
tled shrimp in shell habitat in a laboratory experiment in which prey
consumption crab(-1) was quantified as a function of shrimp density. R
esults of our studies indicate that dense coverage of epibenthic shell
applied to the intertidal site reduced recruitment of ghost shrimp. E
pibenthic shell habitat had significantly fewer YOY shrimp than bare m
udflat at peak settlement and 10 mo post-settlement, and significantly
fewer shrimp than 'subsurface shell' at 10 mo post-settlement. Succes
sful colonization of 'subsurface shell' suggests that shrimp postlarva
e settled preferentially in areas of the shell plot covered with mud o
r possibly were exposed to lower levels of predation than in contiguou
s epibenthic shell areas. Results of the field experiment revealed tha
t 2 to 5 times fewer shrimp postlarvae settled in shell than mud treat
ments; a similar but non-significant trend of lower settlement in shel
l than mud substrate was observed in the laboratory habitat-choice exp
eriment. YOY Dungeness crabs preyed on shrimp in the laboratory experi
ment; prey density had a significant effect on consumption rates but n
ot on proportional shrimp mortalities. In sum, although other processe
s most likely contributed to patterns of YOY shrimp distribution, post
larval habitat selection for mud substrate was a key determinant of re
cruitment success. Recruitment patterns may be further modified by pos
t settlement mortality of YOY shrimp in shell due to YOY Dungeness cra
b predation.