Rodney A. Rountree

Fauna of polyhaline subtidal marsh creeks in Southern New Jersey: Composition, abundance and biomass

Three polyhaline subtidal marsh creeks in southern New Jersey were sampled with weirs and seines to determine seasonal patterns of utilization by fishes and macroinvertebrates. Sixty-four species of fish, 13 invertebrates, and the diamondback terrapin were collected in 69 weir and 57 seine samples from April to November 1988 and April to October 1989. Average abundance, biomass, and faunal composition were strongly seasonal with greatest abundances during spring and summer, and peaks in May and August. Sixteen species were represented by all life-history stages, including the five most important species by combined ranks of percent frequency, mean abundance, and mean biomass. These five species were important during spring, summer, and fall and included the fishes Menidia menidia and Fundulus heteroclitus, the shrimps Palaemonetes vulgaris and Crangon septemspinosa, and the crab Callinectes sapidus. In addition, there were distinct seasonal assemblages of other species which utilized the creeks primarily as young-of-the-year. Importnat species in spring collections included the fishes Clupea harengus, Alosa aestivalis, Alosa pseudoharengus, Pollachius virens, and Urophysics regia, while Leiostomus xanthurus, Pomatomus saltatrix, Paralichthys dentatus, Mugil curema, and Strongylura marina were important in the summer. Fall samples were best characterized by declining abundances of summer species. Thus, subtidal marsh creeks in southern New Jersey appear to be valuable nurseries for a variety of species which spawn over the continental shelf, as well as one of the most important habitats for estuarine residents.

Salt Marsh Ecosystem Support of Marine Transient Species

One of the most important reasons stated in legislation for protecting salt marshes is their support of commercially and recreationally important nekton (fish and crustaceans). Yet, there is a surprising level of uncertainty among scientists regarding the role of salt marshes in supporting secondary production. The emphasis has been on “marine transient” species (in earlier literature often referred to as “estuarine dependent”) because they have life histories that seem designed to place young-of-the-year or juveniles in marsh habitats and because these species are often of commercial or recreational value. Salt marshes are believed to provide: 1) trophic support resulting in high growth rates, 2) increased survivorship due to lowered mortality, and 3) a suitable physico-chemical environment for development of young fishes. In this paper, we consider the evidence for each of these, with an emphasis on the trophic and survivorship aspects. The seasonally warmer temperatures of estuaries and salt marsh creeks apparently provide a metabolic advantage that supports high growth rates. The influence of marsh-derived organic matter in estuarine food webs is apparent, and its importance to marine transient fishes is supported by dietary, behavioral, and isotopic evidence. The major pathways by which marsh organic matter is transferred to fish are largely indirect, through microbial and invertebrate intermediaries. Invertebrates are the primary link to fish consumers of marsh-associated production, transforming microphytes, organic detritus, and microbial detrital heterotrophs into available biomass. Although most detrital organic carbon entering salt marsh systems, mainly from emergent grasses, is apparently respired by heterotrophs, the support of consumers by marsh plant detritus and microalgae can be equally important. The use of salt marsh detritus in food webs usually occurs in close proximity to the salt marsh indicating that outwelling of salt marsh organic matter offshore is not the dominant way that salt marshes support offshore fisheries. Salt marsh support of offshore fisheries is more probably by direct export of juvenile fish biomass and a trophic relay involving ontogenetic and cyclic migrations of nekton species, rather than export of organic detritus. Understanding the controls on marine transient fish mortality is probably the most problematic and least studied aspect of their ecology. The few estimates of mortality rates of fishes in estuaries are as high as, or higher than, mortality rates of fishes in other marine and freshwater ecosystems. However, because of faster growth rates, fish spend less time in the small stages with the higher mortality rates. Within estuaries, mortality rates for some species, but not all, are lower in marsh creeks compared to more open areas. The value of marshes as refuge habitat is probably due to the interaction of temperature, turbidity, and vegetative structure in restricting the foraging of piscine predators.

Listening to Fish

Abstract Passive acoustics is a rapidly emerging field of marine biology that until recently has received little attention from fisheries scientists and managers. In its simplest form, it is the act of listening to the sounds made by fishes and using that information as an aid in locating fish so that their habitat requirements and behaviors can be studied. We believe that with the advent of new acoustic technologies, passive acoustics will become one of the most important and exciting areas of fisheries research in the next decade. However, a widespread lack of familiarity with the technology, methodologies, and potential of passive acoustics has hampered the growth of the field and limited funding opportunities. Herein, we provide an overview of important new developments in passive acoustics together with a summary of research, hardware, and software needs to advance the field.

Foraging Habits, Growth, and Temporal Patterns of Salt-Marsh Creek Habitat Use by Young-of-Year Summer Flounder in New Jersey

Abstract Summer flounder Paralichthys dentatus were collected from intertidal and subtidal polyhaline marsh creeks in the Great Bay–Little Egg Harbor estuarine system in southern New Jersey during 1987–1990 to determine seasonality, duration of creek use by individuals, emigration rate, foraging habits, and daily growth rate of young-of-year fish in those habitats. Four hundred fifty-eight age-0 individuals (mean total length [TL], 238 mm; range, 156–312 mm) were collected from a combination of weir, seine, gill-net, and gig sampling. They were available to the collecting gear from late July through October, peaking numerically in September. Sixty-three (39%) of 162 tagged age-0 summer flounder were recaptured at least once during August–September. The average period of creek use was estimated at 17 d (range, 5–38 d) from release. Decline in percent recaptures suggested an emigration rate of 1.0%/d and 100% emigration within 50 d of release during August–October. Summer flounder appear to undergo tidal mo...

Passive Acoustics as a Tool in Fisheries Science

Abstract Many fishery biologists that are interested in documenting fish habitat and following the movements and behavior of fishes use acoustic tags. Because over 700 fish species naturally produce low-frequency, species-specific sounds, these can be used as natural acoustic tags. Passive acoustic approaches (monitoring sound-producing fishes with hydrophones) show great promise for gathering data in a noninvasive and continuous manner. In this special section, authors review past studies and contribute new findings based on the concept of passive acoustics, in which the sounds produced by fish are used to identify the species present and quantify their relative abundance. Fish have long been known to produce low-frequency sounds, especially members of the families Sciaenidae, Gadidae, Ictaluridae, Cyprinidae, Batrachoididae, Haemulidae, Lutjanidae, and Serranidae. Passive acoustic methods include the use of low-frequency hydrophones, digital recorders, autonomous recording sonobuoys and data loggers, an...

Sounds Produced by the Striped Cusk-Eel Ophidion marginatum (Ophidiidae) during Courtship and Spawning

at night, on 23 July 1989, by otter trawl in Great Bay, New Jersey, and placed in a tank (1.2 m X 1.2 m X 0.9 m) with 15 cm of sand substrate. Tank contents were maintained at ambient bay water temperatures (21.5-27.5 C) and salinity (23-31 ppt) with flow-through seawater at the Rutgers University Marine Field Station. Fish were fed marsh grass shrimp (Palaemonetes vulgaris) daily. Observations were made beginning at sunset until approximately three hours after sunset from 23 July 1989 to 22 September 1989. Behavioral observations were facilitated by a red light over the tank and occasionally flashlights to observe spawning behavior. There were six males (160-193 mm TL) and three females (225-263 mm TL). Sounds were recorded in air using a Panasonic Equalizer 8-Combination Stereo Recorder using the built-in microphone. Sounds were digitized at 22 kHz and analyzed with SoundEdit Pro (Macromedia, Inc.) and SIGNAL (Engineering Design). Number of pulses and pulse periods (msec from beginning of first pulse to beginning of last pulse/number of pulses 1) were calculated for each sound. Although recordings in air outside aquaria are likely to distort individual pulse characteristics from reflections (including pulse length and frequency), the number of pulses and pulse period will be unaffected.

SONIFEROUS BEHAVIOUR OF THE STRIPED CUSK-EEL OPHIDION MARGINATUM

Kenyon, T.N., Ladich, F. & Yan, H.Y. (1998) A comparative study of hearing ability in fishes: the auditory brainstem response approach. J. Comp. Physiol. A 182, 307-318. Ladich, F. & Yan, H.Y. (1998) Correlation between auditory sensitivity and vocalisation in anabantoid fishes. J. Comp. Physiol. A 182, 737-746. Lobel, P.S. (1998) Possible species specific courtship sounds by two sympatric cichlid fishes in Lake Malawi, Africa. Environ. Biol. Fish. 33, 443-452. Tavolga, W.N. (1974) Signal/noise ratio and the critical band in fishes. J. Acoust. Soc. Am. 55, 1323-1333.

SOUNDS OF WESTERN NORTH ATLANTIC FISHES—DATA RESCUE

whether the egg mass simply falls out or is rubbed off. The egg mass is positively buoyant and composed of a transparent gelatinous mass rolled up in a scroll configuration (Fahay 1992). The egg mass gradually expands and breaks up and dissipates after 24 hours, after which time the eggs float freely until larvae begin hatching at about 36 hours. The gelatinous egg mass bears a striking superficial resemblance to a ctenophore floating in the water, suggesting a possible mimicry. However, we hypothesise that the gelatinous egg mass may instead be an adaptation to increase fertilisation success and allows daily spawning with low sperm volume.

Passive acoustic detection of modulated underwater sounds from biological and anthropogenic sources

This paper describes an algorithm for the automatic detection of a particular class of underwater sounds, using a single hydrophone. It is observed that many life-forms, systems or mechanisms emit distinctive acoustic signatures which are characterized by packets of relatively high frequency sound that are repeated at regular, low frequency intervals. These types of sounds are commonly produced by biological (e.g. fishes and invertebrates) and anthropogenic (e.g. scuba diver) sources. The algorithm exploits a simple feature, extracted from the raw hydrophone signal, which enables robust detection even in conditions of severe background noise. In order to demonstrate how the algorithm can be used, trial applications are presented for the detection of two different kinds of underwater sound source. First, the algorithm is applied to the problem of detecting soniferous fish sounds, showing that it is possible to robustly automate the detection of instances of cusk-eel presence in hydrophone recordings, thereby simplifying the arduous task of human monitoring of long sound recordings in marine biological research. Second, the algorithm is applied to the problem of automatic diver detection in a noisy urban estuary, demonstrating its potential for harbor security and fleet protection.

Large vertical movements by a goosefish, Lophius americanus, suggests the potential of data storage tags for behavioral studies of benthic fishes

The extensive periodic vertical movements of up to 14 h and 209 m observed in this study for an individual goosefish, Lophius americanus, challenges previous assumptions about the benthic and highly sedentary behavior of the species as well as of other lophiids. Researchers should consider conducting similar data storage tagging studies with other benthic fishes to test assumptions of sedentary behavior.