John Mark Dean

The utilization of an intertidal salt marsh creek by larval and juvenile fishes: Abundance, diversity and temporal variation

The utilization of an intertidal salt marsh creek in South Carolina during January 1977 was determined by sampling every third ebb tide for 13 days. All fishes leaving the creek during that period were captured in a channel net. This procedure produced a time-series of samples which permitted analysis of the fish community occupying the intertidal creek at all times of day and night.A total of 14,730 larval, juvenile, and adult fishes comprising at least 22 species in 16 families were collected. The most common larval and juvenile fishes wereLeiostomus xanthurus, Mugil spp.,Myrophis punctatus leptocephali,Lagodon rhomboides, Paralichthys spp., andMicropogon undulatus. Catch sizes for all species varied widely between samples. No diurnal-nocturnal pattern in catches was evident forL. xanthurus, Mugil spp.,L. rhomboides andM. undulatus. M. punctatus was taken in large numbers only when the flood tide occurred during the day, while moreParalichthys spp. larvae were taken in late afternoon-evening flood tide samples. The most common invertebrate,Palaemonetes pugio, was taken in large quantities only in late afternoon-night flood tide samples.Three diversity indices were computed for each sample. Values for all indices varied widely between successive samples.The results emphasize a high degree of utilization of the intertidal creek habitat by larval and juvenile fishes. The diurnal-nocturnal activity patterns of some species, and the wide variation in catch size of the other species can permit use of the intertidal salt marsh habitat with reduced competition for available space and energy.

The abundance of estuarine larval and juvenile fish in a South Carolina intertidal creek

The fall and winter population of larval fish in a small intertidal creek was measured. The creek was blocked at high tide, and the immature fish were captured in a channel net designed for consistent quantitative sampling as they left with the ebbing tide. A total of 573,739 individuals with a biomass (preserved wet weight) of 66.1 kg were captured during the eight month sampling period (October 1974–May 1975). Twelve families, 13 genera, and 16 species were represented, with five species comprising 99.3% of the fish captured. The five species were:Leiostomus xanthurus (53.5%),Lagodon rhomboides (31.7%),Brevoortia tyrannus (11.9%),Micropogon undulatus (1.7%), andMyrophis punctatus (0.5%). The net was efficient, the catch was seasonal, and the greatest larval abundance occurred in February and March.

The ultrastructure of the otolithic membrane and otolith in the juvenile mummichog, Fundulus heteroclitus†

The sagitta otolithic membrane of Fundulus heteroclitus consists of two different zones. A structured zone (gelatinous layer), which usually exhibits a reticulated or honeycomb‐like architecture, is composed of tightly arranged fibrous material and covers only the sensory region of the macula. The gelatinous layer extends from the otolith surface to the tips of the sensory hairs, and probably functions primarily as a mechanoreceptor. The arrangement of this zone is closely associated with specific overlying structural features of the otolith surface and may also influence the pattern of mineral deposition to some degree. A nonstructured zone (subcupular meshwork) consists of fibers in very loose networks and covers both sensory and nonsensory regions of the macula. Over the sensory region, some of this fibrous material extends from the epithelial surface, through pores in the gelatinous layer, to the surface of the overlying otolith. In the nonsensory region, fibers of the subcupular meshwork are relatively more numerous and extend around the peripheral margin of the otolith. Evidence is presented which suggests that the fibrous material of the subcupular meshwork is incorporated into the otolith as an organic matrix constituent. New aspects on the ultrastructure of the otolith are presented and discussed.

Calcein as a Fluorescent Marker of Otoliths of Larval and Juvenile Fish

Abstract Calcein is a fluorescent compound that can bind with alkaline earth metals, such as calcium. Upon binding, an increase in fluorescence under ultraviolet light results. Therefore, calcein was evaluated as potentially useful for creating a fluorescent mark in the otoliths of larval and juvenile fish. Such a mark was produced in the sagittae of larvae and juveniles of three species of estuarine fishes after a 2-h immersion in a solution of 125 mg/L in seawater. The mark was easily distinguished under ultraviolet epifluorescent microscopy. This technique provides an alternative to the use of tetracycline in age and growth studies.

Diurnal rhythm in otolith formation in the goldfish, Carassius auratus

Abstract 1. 1. The presence of diurnal rhythm in otolith formation was examined physiologically in the goldfish, Carassius auratus . 2. 2. 45 Ca uptake by otoliths indicated that otolith formation slowed down or stopped at sunrise and resumed in 3 hr. 3. 3. Plasma calcium level increased toward sunrise and fell significantly in the next 3 hr. 4. 4. The increasing phase of plasma calcium corresponded to the period of rapid decrease in 45 Ca in the culture medium.

Use of fish communities to assess environmental impacts in South Carolina coastal plain streams

Abstract We developed an index of biotic integrity (IBI) and a biotic index based on fish species richness (FSBI) to assess the ecological health of streams on the Savannah River Site, a 780-km2 U.S. Department of Energy facility located in the Sand Hills ecoregion on the upper coastal plain of South Carolina. To maintain the responsiveness of the IBI to a variety of impacts yet incorporate sufficient ecoregion specificity to achieve acceptable accuracy, we included metrics from each of six metric categories proven useful in other ecoregions (species number, species composition, trophic composition, local indicator species, fish abundance, and fish condition) but selected specific metrics within each category based on their ability to discriminate between disturbed and undisturbed sites in the Sand Hills ecoregion. We also developed a procedure based on species–area curves to remove the potentially confounding effects of site-specific differences in sample unit size and sampling effort from species number...

Scanning electron microscope observations of the organic matrix in the otolith of the teleost fish Fundulus heteroclitus (Linnaeus) and Tilapia nilotica (Linnaeus)

Abstract Scanning electron microscope observations of sagitta otoliths of Fundulus heteroclitus (Linnaeus) and Tilapia nilotica (Linnaeus) have revealed that the “discontinuous zone” is a narrow band of organic matrix consisting of fibers ≈900 A thick, that in turn are composed of thin fibers ≈200 A thick. The “incremental zone” is the crystalline layer with crystals elongated perpendicular to the otolith periphery that are usually terminated at the discontinuous zones. The crystals are embedded in organic matrix fibers that appear similar to and continuous with the fibers of the discontinuous zones. Frequently, these fibers aggregate into matrix sheets. Based on these findings, a possible process of otolith formation is proposed.

Immersion marking of larval and juvenile hatchery-produced striped bass with oxytetracycline

Abstract Larval and juvenile striped bass Morone saxatilis were mass-marked by oxytetracycline immersion as part of normal hatchery procedures. In 1988, 70% of samples of 1.2 million juveniles treated en route to stocking had a fluorescent mark in their otoliths. In 1989, all samples of 7 million larvae (6–9 d old) treated during transport to grow-out ponds had marked otoliths. Marks were retained for at least 5 and 7 months by larvae and juveniles, respectively. There was no significant difference between the mortality rates of marked and unmarked larvae to 30 d after hatch.

An examination of sexual dimorphism in Atlantic and Pacific blue marlin using body weight, sagittae weight, and age estimates☆

Abstract Length, weight and otoliths of Atlantic and Pacific blue marlin ( n = 436) were sampled between 1979 and 1983 in the Atlantic and Pacific Oceans from recreational landings. Otolith weight was highly variable within size classes, but the range of otolith weights was the same for males and females from both oceans. Although age estimates for Atlantic and Pacific blue marlin were not validated, males and females were estimated to be equally long-lived, reaching estimated ages of >20 yr, yet females achieve much larger somatic sizes than males. Length was not useful in predicting estimated age. The sex-related size differences in Atlantic and Pacific blue marlin can be attributed to differential growth between sexes. Although males can grow to a maximum size of ∼ 160 kg and females grow to at least 540 kg, longevity was similar for both sexes. The sex-related size differences in blue marlin are related to differential growth between sexes and are not due to differential mortality. Otolith weight was linearly related to estimated age and r 2 ranged from 0.70 to 0.91 for Atlantic and Pacific blue marlin. This relationship demonstrates potential for estimating the age structure of the landings, if validation of the aging method can be achieved.

Migration and feeding of the predatory fish, Bairdiella chrysura Lacépède, in an intertidal creek

Abstract Juvenile Bairdiella chrysura (Lacepede) (silver perch) were collected hourly from a South Carolina intertidal creek for 10 tidal cycles. Stomach content analyses suggest that silver perch feed nocturnally within the intertidal zone during high tide. The reasons for this feeding behavior are discussed with emphasis on the importance of intertidal areas as regions where energy is transferred from the marsh to the estuary.