Development of grunts and snappers of southeast Florida: Cross-shelf distributions and effects of beach management alternatives

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Marine Biology and Fisheries

First Committee Member

Jerald S. Ault, Committee Chair


The economically important fish families Haemulidae and Lutjanidae (grunts and snappers) are valuable model systems for the comparative examination of development and habitat use. Over 20 species were used to assess: (a) variations in early life history attributes within and among basal percoid families, and (b) effects of ten beach management alternatives in southeast Florida. Diagnostic developmental patterns were determined for early demersal stages of 21 species with an emphasis on field identification. Daily deposition of otolith increments was verified for four species of grunts and snappers. Mean growth ranged from 0.35 to.63 mm$\cdot$d$\sp{-1}$ for seven grunt species and from 0.68 to 0.94 mm$\cdot$d$\sp{-1}$ for five snapper species. An otolith mark associated with settlement was identified in six species of snappers. Mean ages of settlement were from 31 to 42 days in snappers, twice those of grunts. A hierarchical cross-shelf habitat (CSH) framework was developed to characterize structural habitats within and among larger cross-shelf strata. For the Biscayne Bay region, combining habitats and cross-shelf strata within CSH matrices identified over 150 available habitats. An opportunistic strategy of both estuarine and reef usage characterized early stages of approximately ten species. Eleven species were considered reef-dependent. Five to six species, primarily snappers, were estuarine-dependent. Faunal shifts into urbanized estuaries by reef species are being induced by channelization, replacement of vegetation with hard structures, and other factors.Fishes of nearshore hardbottom reefs were quantified at three sites over a two-year period using random, 2 x 15 m visual transects. Eighty-two species were censused from 32 families at all sites pooled. Grunts were the most diverse family, with 11 species recorded. Early life stages represented over 80% of the total individuals at all sites. After 1 yr, dredging burial of the nearshore hardbottom site significantly lowered the abundances of species and individuals. Approximately 192 species of fishes within 62 families are now recorded from nearshore hardbottom of east Florida. Beach management effects upon coastal fishes were further examined by characterizing stressors and effects among ten policy alternatives using a ecological risk assessment framework and a 170-year database of past and future projects. Forty-seven dredge projects in the last 37 years have deposited $48\times10\sp6$ yd$\sp3$ of mid-shelf sediments within an intertidal/subtidal corridor of 500 ft x 110 miles in southeast Florida. At least $80\times10\sp6$ additional yd$\sp6$ of sediments are planned for deposition within the same corridor in the next 50 years. Despite naturally dynamic populations may occur nearshore conditions, reductions in the recruitment of local fish via dredge burial of reefs prior to and during seasonal peaks in settlement. The assumption that large dredge projects are environmentally benign in subtropical coastal waters is premature. Multicriteria decision-support procedures identified combinations of several options (e.g., increased inlet sand bypassing, proactive mitigation), in addition to dredging, as technically and politically feasible for improved environmental management of South Florida's beach systems.


Biology, Oceanography; Environmental Sciences

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