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C.C. McIvor

Publications and source records attributed to C.C. McIvor.

12 recordsLinked to original sources
USGS2010

Modifications to the bottomless lift net for sampling nekton in tidal mangrove forests

Sampling fishes in vegetated intertidal wetlands is logistically challenging. We modified the 2 ?? 3-m2 bottomless lift net developed for sampling nekton (fish and decapod crustaceans) on the surface of salt marshes for use in tidal mangrove forests with a woody (as opposed to herbaceous) underground root system. As originally designed (Rozas, Mar Ecol Prog Ser 89:287-292, 1992), the lift net was buried directly in the marsh substrate. The net was raised at slack high tide thereby encircling nekton within the enclosed area. A chain-line on the net bottom prevented escape under the net once deployed. However, when we used this same design in tidal mangrove forests, the extensive woody roots and occasional slumping sediments resulted in uneven trenches that could not be cleared effectively during sample recovery. We made 3 modifications to the original net design: (i) lined the peat trenches with aluminum channels of uniform width and depth; (ii) replaced the previous chain-line with Velcro closures that directly attached the net to the inner face of the outer wall of the aluminum channel; and (iii) removed the subtidal pan previously used for concentrating the enclosed nekton at low tide, and filled in those depressions with on-site peat. In the modified version, the aluminum trench became the only subtidal refuge available to nekton, and it was from here that we collected the sample after the forest drained. These modifications permitted high clearing efficiency (93-100%) of fin-clipped individuals of two common species of estuarine resident fishes, Kryptolebias marmoratus (mangrove rivulus) and Bathygobius soporator (frillfin goby). Additionally, the density estimates of grass shrimp (Palaemonetes spp.) increased 10-fold post-modification. ?? 2010 US Government.

Wetlands Ecology and Management↗
USGS2008

Demography and ecology of mangrove diamondback terrapins in a wilderness area of Everglades National Park, Florida, USA

Diamondback Terrapins (Malaclemys terrapin) are distributed in brackish water habitats along the U.S. east coast from Massachusetts to Texas, but many populations may be in decline. Whereas ample morphological, behavioral, and reproductive information has been collected for terrapins living in temperate salt marsh habitats, comparatively little is known about mangrove terrapins. To understand population structure of mangrove M. terrapin living in a wilderness area, we conducted a capture-recapture study in the remote, protected Big Sable Creek complex of Everglades National Park, Florida. The goals of the study were to collect baseline demographic data and to compare population structure and growth rates of mangrove terrapins with what is known for more well studied salt marsh terrapins in locations that experience human-imposed threats. We marked 300 terrapins; the sex ratio was 1 female:1.2 males. Considerable sexual size dimorphism was apparent, with reproductively mature females three times larger (by mass) than mature males. Eighty percent of females and 94% of males were classified as mature, based on straight plastron length (SPL). For a subset of terrapins not yet at maximum size (n = 39), we measured growth as a change in straight carapace length over time of 0.3-26.4 mm/yr for females (n = 26) and 0.9-14.5 mm/yr for males (n = 13). Our study presents the first demographic data on mangrove M. terrapin in the coastal Everglades. ?? 2008 by the American Society of Ichthyologists and Herpetologists.

Copeia↗
USGS2008

Range expansion of the Mayan cichlid, cichlasoma urophthalmus (pisces, cichlidae), above 28°N in Florida

Introduced exotic species are a well-recognized problem in Florida's subtropical ecosystems. The presence of the exotic Mayan cichlid (Cichlasoma urophthalmus) was first confirmed in Florida in 1983, when numerous individuals were found in the northeastern Florida Bay. Since then, this species has continued to expand its range northward. The capture, beginning in October 2004 to present, of large numbers of Mayan cichlids from central Florida's east- and west-coast mangrove systems north of 28°N latitude is documented here. Mayan cichlids in a wide range of sizes (estimated ages 0-7 years) at both east- and west-coast sites were collected. In addition, macroscopic examination of gonads showed the presence of developing eggs. The occurrence of multiple age-classes, maturing individuals, cichlid nests, and juveniles, plus repeated collections over a four-year period, indicates that the Mayan cichlid is successfully reproducing and surviving the average winter temperatures in some estuarine waters in central Florida.

Florida↗
USGS2007

An assessment of ichthyofaunal assemblages within the mangal of the Belize offshore cays

We assessed ichthyofaunal diversity within offshore mangrove cays in Belize during three, 2-wk surveys (2003, 2004, 2005). Nine sampling gears were deployed in pre-defined micro-habitats: fringe, transition, dwarf red mangrove, internal creeks, ponds, and sinkholes. Water quality data (temperature, salinity, DO) were taken during most collections. A total of 2586 gear sets was completed and 8131 individuals collected, comprising 75 taxa. Minnow trap data from the various micro-habitats tested indicates some overlap in assemblages. Significant differences in water quality were also noted, with the fringe representing the most benign and the sink-hole the most harsh microhabitats, respectively. We also conducted extensive visual surveys around the fringe at a number of cays, tallying an additional 67 taxa. The fringe is the most diverse (128 taxa) and sinkhole least (12 species). An overall total of 142 taxa from 55 families has therefore been documented from the cays, and all but eight were found on Twin Cays alone. This figure is among the highest reported for oceanic mangroves in this biogeographic realm. Our comprehensive approach with a variety of gear-types in a wide range of micro-habitats, combined with visual observation, lends credence to the conclusion that most ichthyological species inventories for the mangal are commonly underestimates.

Bulletin of Marine Science↗
USGS2007

Mangrove removal in the belize cays: effects on mangrove-associated fish assemblages in the intertidal and subtidal

We investigated the effects of mangrove cutting on fish assemblages in Twin Cays, Belize, in two habitat types. We conducted visual censuses at two sites in adjoining undisturbed/disturbed (30%–70% of shoreline fringe removed) sub-tidal fringing Rhizophora mangle Linnaeus, 1753. Observers recorded significantly more species and individuals in undisturbed sites, especially among smaller, schooling species (e.g., atherinids, clupeids), where densities were up to 200 times greater in undisturbed habitat. Multivariate analyses showed distinct species assemblages between habitats at both sites. In addition, extensive trapping with wire minnow traps within the intertidal zone in both undisturbed and disturbed fringing and transition (landward) mangrove forests was conducted. Catch rates were low: 638 individuals from 24 species over 563 trap-nights. Trap data, however, indicated that mangrove disturbance had minimal effect on species composition in either forest type (fringe/transition). Different results from the two methods (and habitat types) may be explained by two factors: (1) a larger and more detectable species pool in the subtidal habitat, with visual "access" to all species, and (2) the selective nature of trapping. Our data indicate that even partial clearing of shoreline and more landward mangroves can have a significant impact on local fish assemblages.

Twin Cays↗
USGS2006

Habitat selection by three littoral zone fishes: effects of predation pressure, plant density and macrophyte type

We conducted laboratory experiments which demonstrated that three littoral zone fishes differentially selected among three macrophytes when seeking refuge from predation. In the presence of a predator (a juvenile Micropterus salmoides ), mosquitofish ( Gambusia holbrooki ), sailfin mollies ( Poecilia latipinna ). and dollar sunfish ( Lepomis marginatus ) displayed ferential use of four tank areas containing patches of either Hydrilla verticillata , Potamogeton illinoensis, Panicum hemitomon , or no plants. Patterns habitat selection, and the consistency of these patterns among replicates, differed among the three fishes and among three plant-density treatments - natural (each macrophyte presented at its mean field density), equal (all three macrophytes at the same density), and control (no plants). Selection for H. verticillata by mosquitofish was significant for both the equal and natural treatments, and thus was not caused by differences in plant density alone. Sailfin mollies displayed significant selection for H. verticillata only in the natural plant-density treatments. Dollar sunfish showed less consistent habitat selection than either mosquitofish or sailfin mollies. Significant habitat selection was not found in the absence of a predator, and there was no evidence for lection among the tank areas in control treatments. Patterns of habitat selection by the three fishes in our laboratory study corresponded to observed habitat use in Lake Okeechobee.

Ecology of Freshwater Fish↗
USGS2006

Spatial patterns of fish communities along two estuarine gradients in southern Florida

In tropical and subtropical estuaries, gradients of primary productivity and salinity are generally invoked to explain patterns in community structure and standing crops of fishes. We documented spatial and temporal patterns in fish community structure and standing crops along salinity and nutrient gradients in two subtropical drainages of Everglades National Park, USA. The Shark River drains into the Gulf of Mexico and experiences diurnal tides carrying relatively nutrient enriched waters, while Taylor River is more hydrologically isolated by the oligohaline Florida Bay and experiences no discernable lunar tides. We hypothesized that the more nutrient enriched system would support higher standing crops of fishes in its mangrove zone. We collected 50 species of fish from January 2000 to April 2004 at six sampling sites spanning fresh to brackish salinities in both the Shark and Taylor River drainages. Contrary to expectations, we observed lower standing crops and density of fishes in the more nutrient rich tidal mangrove forest of the Shark River than in the less nutrient rich mangrove habitats bordering the Taylor River. Tidal mangrove habitats in the Shark River were dominated by salt-tolerant fish and displayed lower species richness than mangrove communities in the Taylor River, which included more freshwater taxa and yielded relatively higher richness. These differences were maintained even after controlling for salinity at the time of sampling. Small-scale topographic relief differs between these two systems, possibly created by tidal action in the Shark River. We propose that this difference in topography limits movement of fishes from upstream marshes into the fringing mangrove forest in the Shark River system, but not the Taylor River system. Understanding the influence of habitat structure, including connectivity, on aquatic communities is important to anticipate effects of construction and operational alternatives associated with restoration of the Everglades ecosystem.

Florida↗
USGS2001

Effects of a test flood on fishes of the Colorado River in Grand Canyon, Arizona

A beach/habitat-building flow (i.e., test flood) of 1274 m 3 /s, released from Glen Canyon Dam down the Colorado River through Grand Canyon, had little effect on distribution, abundance, or movement of native fishes, and only short-term effects on densities of some nonnative species. Shoreline and backwater catch rates of native fishes, including juvenile humpback chub ( Gila cypha ), flannelmouth suckers ( Catostomus latipinnis ), and bluehead suckers ( C. discobolus ), and all ages of speckled dace ( Rhinichthys osculus ), were not significantly different before and after the flood. Annual spring spawning migrations of flannelmouth suckers into the Paria River and endangered humpback chub into the Little Colorado River (LCR) took place during and after the flood, indicating no impediment to fish migrations. Pre-spawning adults staged in large slack water pools formed at the mouths of these tributaries during the flood. Net movement and habitat used by nine radio-tagged adult humpback chub during the flood were not significantly different from prior observations. Diet composition of adult humpback chub varied, but total biomass did not differ significantly before, during, and after the flood, indicating opportunistic feeding for a larger array of available food items displaced by the flood. Numbers of nonnative rainbow trout ( Oncorhynchus mykiss ) <152 mm total length decreased by ∼8% in electrofishing samples from the dam tailwaters (0–25 km downstream of the dam) during the flood. Increased catch rates in the vicinity of the LCR (125 km downstream of the dam) and Hell's Hollow (314 km downstream of the dam) suggest that these young trout were displaced downstream by the flood, although displacement distance was unknown since some fish could have originated from local populations associated with intervening tributaries. Abundance, catch rate, body condition, and diet of adult rainbow trout in the dam tailwaters were not significantly affected by the flood, and the flood did not detrimentally affect spawning success; catch of young-of-year increased by 20% in summer following the flood. Post-flood catch rates of nonnative fathead minnows ( Pimephales promelas ) in shorelines and backwaters, and plains killifish ( Fundulus zebrinus ) in backwaters decreased in the vicinity of the LCR, and fathead minnows increased near Hell's Hollow, suggesting that the flood displaced this nonnative species. Densities of rainbow trout and fathead minnows recovered to pre-flood levels eight months after the flood by reinvasion from tributaries and reproduction in backwaters. We concluded that the flood was of insufficient magnitude to substantially reduce populations of nonnative fishes, but that similar managed floods can disadvantage alien predators and competitors and enhance survival of native fishes.

Arizona↗
USGS1997

A rop net and removable walkway used to quantitatively sample fishes over wetland surfaces in the dwarf mangrove of the Southern Everglades

We describe a 9 m 2 drop net and removable walkways designed to quantify densities of small fishes in wetland habitats with low to moderate vegetation density. The method permits the collection of small, quantitative, discrete samples in ecologically sensitive areas by combining rapid net deployment from fixed sites with the carefully contained use of the fish toxicant rotenone. This method requires very little contact with the substrate, causes minimal alteration to the habitat being sampled, samples small fishes in an unbiased manner, and allows for differential sampling of microhabitats within a wetland. When used in dwarf red mangrove ( Rhizophora mangle ) habitat in southern Everglades National Park and adjacent areas (September 1990 to March 1993), we achieved high recovery efficiencies (78&ndash;90%) for five common species <110 mm in length. We captured 20,193 individuals of 26 species. The most abundant fishes were sheepshead minnow Cyprinodon variegatus , goldspotted killifish Floridichthys carpio , rainwater killifish Lucania parva , sailfin molly Poecilia latipinna , and the exotic Mayan cichlid Cichlasoma urophthalmus . The 9 m 2 drop net and associated removable walkways are versatile and can be used in a variety of wetland types, including both interior and coastal wetlands with either herbaceous or woody vegetation.

Wetlands↗
USGS1997

Effects of fish density and river fertilization on algal standing stocks, invertebrates communities, and fish production in an Arctic River

This study examined the relative importance of bottom-up and top-down controls of an arctic stream food web by simultaneous manipulation of the top predator and nutrient availability. We created a two-step trophic system (algae to insects) by removal of the top predator (Arctic grayling, Thymallus arcticus) in fertilized and control stream reaches. Fish abundance was also increased 10 times to examine the effect of high fish density on stream ecosystem dynamics and fish. We measured the response of epilithic algae, benthic and drifting insects, and fish to nutrient enrichment and to changes in fish density. Insect grazers had little effect on algae and fish had little effect on insects. In both the control and fertilized reaches, fish growth, energy storage, and reproductive response of females declined with increased fish density. Fish growth and energy storage were more closely correlated with per capita insect availability than with per capita algal standing stock

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1995

Difference in the crab fauna of mangrove areas at a southwest Florida and a northeast Australia location: Implications for leaf litter processing

Existing paradigms suggest that mangrove leaf litter is processed primarily via the detrital pathway in forests in the Caribbean biogeographic realm whereas herbivorous crabs are relatively more important litter processors in the Indo-West Pacific. To test this hypothesis, we used pitfall traps to collect intertidal crabs to characterize the crab fauna in a mangrove estuary in southwest Florida. We also tethered mangrove leaves to determine if herbivorous crabs are major leaf consumers there. We compared the results with previously published data collected in an analogous manner from forests in northeastern Australia. The crab fauna in Rookery Bay, Florida, is dominated by carnivorous xanthid and deposit-feeding ocypodid crabs whereas that of the Murray River in northeastern Australia is dominated by herbivorous grapsid crabs. No leaves tethered at five sites in the forests in Southwest Florida were taken by crabs. This contrasts greatly with reported values of leaf removal by crabs in Australian forests of 28-79% of the leaves reaching the forest floor. These differences in the faunal assemblages and in the fate of marked or tethered leaves provide preliminary support for the hypothesis that leaf litter is in fact processed in fundamentally different ways in the two biogeographic realms.

Estuaries↗