Robert E. Schmidt

A Comparison of Alternative Approaches to Discriminate Larvae of Striped Bass and White Perch

Abstract Striped bass Morone saxatilis and white perch M. americana are sympatric in rivers and estuaries across a broad region of eastern North America. Discrimination of their larvae is often an important but problematic component of large ichthyoplankton monitoring programs: their larvae are morphologically similar (particularly at the post-yolk-sac stage) and often co-occur. In a blind test using hatchery-reared larvae of known species identity, we compared the traditional externally based approach (method 1) with three alternatives: an approach based on interdigitation patterns of osteological features of cleared and stained individuals that has shown high potential for post-yolk-sac larvae (method 2); an approach based on premaxillary and vomerine tooth counts (method 3); and a variation of method 2 designed as a key to shorten inspection time (method 4). Method 1 provided the highest overall correct identification rates for striped bass (98.5%) and white perch (96.8%). Internal osteological feature...

Aspects of the life history of a freshwater population of the mummichog, Fundulus heteroclitus (Pisces: Cyprinodontidae), in the Bronx River, New York, U.S.A.

A freshwater population of the mummichog, Fundulus heteroclitus, was sampled during summer and autumn 1979, from the Bronx River, New York. Other occurrences in freshwater of this common estuarine cyprinodontid fish have been noted in Pennsylvania, New Hampshire and Canada. In the Bronx River, this species is a significant part of the fauna and is one of the few species found throughout the river system. Specimens were examined to determine the growth and diet. It appears that this freshwater population does not differ from its brackish water conspecifics with respect to age structure, growth rate and feeding behavior.

Low PCB Concentrations Observed in American Eel (Anguilla rostrata) in Six Hudson River Tributaries

Abstract We analyzed 73 eels, collected in 2004 and 2005 above the head of tide in six Hudson River tributaries, for total PCBs, length, weight, age, and nitrogen stable isotope ratios (δ15N). Mean total PCB concentration (wet weight basis) was 0.23 ppm ± 0.08 (standard error), with a range of 0.008 to 5.4 ppm. A majority of eels (84%) had concentrations below 0.25 ppm, and only seven eels (10%) had concentrations exceeding 0.5 ppm. Those eels with higher PCB concentrations were 12 yr; there was a weak correlation of PCB concentration with δ15N and also with weight. Compared to recent (2003) data from the mainstem of the Hudson River estuary, these results indicate that tributaries are generally much less contaminated with PCBs. We hypothesize that those tributary eels with high PCB concentrations were relatively recent immigrants from the mainstem. Given concern over the possible adverse effects of PCBs on eel reproduction, these tributaries may serve as refugia. Therefore, providing improved access to upland tributaries may be critically important to this species.

Variation in Barbels of Rhinichthys cataractae (Pisces: Cyprinidae) in Southeastern New York with Comments on Phylogeny and Functional Morphology

ABSTRACT Large variation in presence and size of barbels and development of barbel papillae in longnose dace (Rhinichthys cataractae) is described. Larger dace seemed to have larger barbels and more papillae but the correlation coefficients for these relationships are low. Barbels are not recommended as a character for defining North American minnow genera and should be used with caution in defining species. In longnose dace, the location, morphology, and variation of barbels suggest they do not function as contact taste organs. Alternative functions like orientation towards a food source or intraspecific communication are more compatable with the observed variation. Barbels are not necessarily all homologous and, in the absence of direct evidence, could equally be considered as either an apomorphic (derived) or a pleisiomorphic (primitive) character.

Diet Composition and Feeding Behavior of Larval American Shad, Alosa sapidissima (Wilson), after the Introduction of the Invasive Zebra Mussel, Dreissena polymorpha (Pallas), in the Hudson River Estuary, NY

Abstract The invasive Dreissena polymorpha (Zebra Mussel) has greatly altered the zooplankton community of the Hudson River by reducing the abundance of native zooplankton and inundating the system with its free-swimming veliger larvae. Since the invasion, there has been a reduction in pelagic fishes, including Alosa sapidissima (American Shad), which is thought to be, in part, a result of the decreases in zooplankton populations. To better understand the complex interaction between this mussel species and American Shad, it is important to describe the fishs current larval diet. Although American Shad larvae readily consumed veligers and this food source may contribute to year-class strength, the importance of veligers as a diet item greatly depends on larval—veliger temporal overlap and yearly shifts in veliger abundance, digestibility, and nutrition.

Evidence of Potamodromy in an Estuarine Population of Smallmouth Bass (Micropterus dolomieu)

ABSTRACT Drift of smallmouth bass (Micropterus dolomieu) fry was documented from Stockport Creek, a tributary to the Hudson River estuary, New York. This drift was not correlated with high flow events, very low light levels, high turbidity, or rapid temperature changes normally associated with catastrophic drift. We interpret the smallmouth bass drift in this tributary as normal export of fry spawned by potamodromous adults. The estimated magnitude of drift is large enough to be a significant addition to the estuarine smallmouth bass population.

New distribution records and complementary description of Haemomaster venezuelae (Siluriformes: Trichomycteridae), a rare and poorly known fish from Northern South America

New locations of the rare Haemomaster venezuelae (Pisces: Trichomycteridae) are described. One new record is from the Rio Orinoco, Venezuela, four are from the Essequibo drainage, Guyana.

Observations on Oriental Weatherfish (Misgurnus anguillicaudatus), an Exotic Species in the Hudson River Valley, New York

Abstract We collected data on the distribution, sex, size, fecundity, and food habits of a newly discovered population of Misgurnus anguillicaudatus (Oriental Weatherfish) in the Hudson Valley, NY. Oriental Weatherfish were distributed throughout the Dwaar Kill in Orange and Ulster counties and at least 7 km of the Wallkill River, principally in the soft substrates of stream margins. Males were smaller than females and apparently had shorter life spans. Sexual maturity and spawning attributes were evident. Mature males had pronounced dorsolateral ridges on at least the posterior third of the body, and females exhibited post-spawning abrasions dorsal and anterior to the vent. Female Oriental Weatherfish are batch-spawners producing up to 18,000 eggs at one time. Oriental Weatherfish in the Dwaar Kill consumed a variety of aquatic macroinvertebrates and exhibited generalist feeding habits. This species does not seem to be affecting other vertebrates where currently found, but potential negative interactions with the native Umbra pygmaea (Eastern Mudminnow) merit attention. Monitoring of the Hudson Valley populations is needed to determine if Oriental Weatherfish abundance or range changes dramatically, and to determine if their presence is causing any lasting effects on the ecosystem.

A BENTHIC JUVENILE SCRAWLED COWFISH (ACANTHOSTRACION QUADRICORNIS) FROM THE LOWER HUDSON RIVER ESTUARY

Abstract A small benthic juvenile scrawled cowfish, Acanthostracion quadricornis (Linnaeus 1758), is reported from the Hudson River. A description of this life stage is provided and the specimen is identified as a scrawled cowfish based on several morphological characters.

Aspects of the Life History of the Cutlips Minnow, Exoglossum maxillingua, from two Eastern Pennsylvania Streams

ABSTRACT Two eastern Pennsylvania populations of the cutlips minnow, Exoglossum maxillingua, were studied; one from the Delaware River drainage and the other from the Susquehanna. Specimens were collected by electroshocker during July 1979. Gut content analysis revealed that the cutlips minnow diet varied with age. Major food items included larval trichopterans, especially hydropsychids, and also chironomidlarvae. Cutlips minnows did not exhibit obvious sexual dimorphism outside of their spawning season. Sex ratios tended to emphasize females, presumably related to higher spawning-related mortality among males. Scale analysis and length-frequency showed that individuals ranged up to IV+ years of age, with I+ and II+ age classes predominating. No significant differences between the length-weight relationships of the two populations were evident.