| dc.description.abstract | Studying assemblage patterns of juvenile fishes across ecologically connected habitats
is necessary for understanding connectivity. Mangroves, seagrass beds, and coral
habitats are ecologically essential for the survival of juvenile fishes. These habitats are
connected through various mechanisms related to larval supply, ontogenic feeding,
juvenile migration, and opportunistic adult phases. A mangrove-seagrass-coral reef
continuum on Kenya's south coast was investigated to assess connectivity using
juvenile fish assemblages. Between August 2021 and August 2022, a beach seine was
used to collect samples monthly for two days. Fish species diversity across habitats
was determined using Shannon-Weiner diversity index (H'). Detrended
Correspondence Analysis (DCA) was applied to investigate species associations with
the three habitats. The trophic level of each fish species was obtained from FishBase.
Sea surface temperature and salinity were measured monthly at each site using a YSI
multi-parameter probe. Species associations with temperature and salinity were
assessed using Canonical Correspondence Analysis (CCA). A total of 8,575 fish
specimens representing 228 species from 52 families were recorded. The coral reef
habitat had the most individuals (n = 3,186) and was the most species-rich (168
species), followed by seagrass (2,420 individuals, 132 species) and mangrove (1,783
individuals, 119 species). Significant differences in species diversity were observed
across the habitats during the northeast monsoon (NEM) and the southeast monsoon
(SEM) (p = 0.026). The Kruskall -Wallis test showed no significant differences in the
mean number of individuals per haul across habitats H (2, N = 60) = 4.81, p = 0.090).
It also showed no significant difference in the mean number of individuals per haul
between seasons H(1, N=60) = 2.10, p = 0.150). A two-way ANOVA revealed
significant differences in fish diversity across the habitats (df = 2; f = 5.677; p = 0.006).
Pair-wise comparison using Tukey HSD test revealed differences in species diversity
between the coral and mangrove habitats (p = 0.044), but no significant differences in
species diversity between seasons (df = 1; f = 0.818; p = 0.097). Overall, 69 fish species
were common across the three habitats. DCA results revealed a strong association of
species Pempheris mangula, Yarica hyalosoma, Pristotis obtusirostris, Taeniamia fucata, and
Apogon fragilis to mangrove habitat. CCA results showed a positive relationship with
increased temperature in the mangrove habitat represented by Apogon fragilis and
Taeniamia fucata, while species, such as Siganus luridus and Sphyraena barracuda,
showed a positive relationship with increased salinity in seagrass habitat. The
Kolmogorov-Smirnov (K-S) tests revealed no significant difference in trophic
signatures between the mangrove and seagrass habitat (D = 0.2308; p = 0.4402), but a
significant difference between the mangrove and coral habitat (D = 0.5385; p =
0.00055) as well as between the seagrass and coral habitat (D = 0.4615; p = 0.004906).
This study demonstrates the existence of connectivity across a mangrove-coral
seagrass continuum in Shimoni and recommends long-term studies on nearshore
habitat connectivity for better conservation and management strategies, including
ecosystem-based fisheries management. | en_US |
