Brevoortia Tyrannus Latrobe Research Articles

The diet of Chesapeake Bay striped bass in the late 1950s

AbstractThe diet of Chesapeake Bay striped bass, (Morone saxatilis) Walbaum, based on unpublished stomach content data from 916 fish collected between 1955 and 1959 was described. The diet in the late 1950s, quantified using an index of relative importance (IRI), was dominated by Atlantic menhaden, Brevoortia tyrannus Latrobe. Atlantic menhaden (66%) and bay anchovy, Anchoa mitchilli Valenciennes, (19%) had the highest IRI value overall. Small striped bass (<600 mm total length) ate predominantly bay anchovy (IRI = 67%). Large striped bass (≥ 600 mm total length) ate predominantly Atlantic menhaden (IRI = 93%). Since 1990 small striped bass rely more on invertebrate prey and larger fish now rely more on small pelagic prey, such as bay anchovy and 0‐age clupeids. Analysis of historical data using current techniques provided a valuable tool for comparison to help in understanding the current striped bass predator–prey relationship in Chesapeake Bay.

Predator–prey analysis of striped bass and Atlantic menhaden in upper Chesapeake Bay

AbstractBetween 1997 and 2000, an outbreak of skin lesions and observations of emaciated striped bass, Morone saxatilis (Walbaum), in upper Chesapeake Bay were attributed to a perceived shortage of its main prey, Atlantic menhaden, Brevoortia tyrannus Latrobe. Abundance estimates, Atlantic menhaden consumption per recruit analysis (modified yield‐per‐recruit), bioenergetics analysis and predator–prey theory were combined to explore whether an imbalance between striped bass and Atlantic menhaden in upper Chesapeake Bay was plausible. Reduced fishing mortality and higher size limits that underpinned the effort to restore striped bass during the 1980s and 1990s lead to more abundant and larger striped bass in upper Chesapeake Bay, increasing predatory demand for forage‐sized Atlantic menhaden, the abundance of which declined to a historic low. Nominal losses of age 0–2 Atlantic menhaden to harvest and potential striped bass predation exceeded supply after 1998. The outbreak of lesions in upper Chesapeake Bay striped bass coincided with increased variation in weight‐at‐length, decreased length‐at‐age, and decreased presence of Atlantic menhaden in diets. Decreased attack success, inferred from a 97% decline in ratios of forage‐sized Atlantic menhaden to striped bass between 1983 and 1998, would have expected to have been followed by a deterioration of striped bass nutritional state. Transmission of disease would have been aided by high density of striped bass in poor nutritional condition residing in degraded habitat (Chesapeake Bay was the most hypoxic estuary in the mid‐Atlantic region in the late 1990s). These problems suggest that striped bass exceeded their carrying capacity in Chesapeake Bay during the late 1990s.

Endogenous swimming rhythms of larval Atlantic menhaden, Brevoortia tyrannus Latrobe: Implications for vertical migration

Atlantic menhaden, Brevoortia tyrannus Latrobe, spawn on the continental shelf. Larvae are transported shoreward where they enter estuaries and metamorphose. Field studies suggest that while offshore, larvae may undergo nocturnal diel vertical migration (DVM), in which they are near the surface during the night and at depth during the day. The DVM pattern is more pronounced in estuaries but the timing of the nocturnal ascent may be related to tides. Larvae appear to swim in the water column during nocturnal rising tide and are less abundant at all other times. This migration pattern would result in up-estuary movement by selective tidal stream transport. The present study measured endogenous swimming rhythms of Atlantic menhaden larvae and related them to possible vertical migration patterns in offshore and estuarine areas. Larvae reared in the laboratory on a diel light:dark cycle were measured at three sizes (7–9 mm, 14–17 mm and 23–27 mm total length [TL]) as representative of larvae in offshore areas, while estuarine larvae (25–30 mm TL) were collected in the Newport River Estuary (N.C.). Swimming was monitored in a column under constant conditions in the laboratory with a time-lapse video system. In all cases, larvae had a similar circadian rhythm. The smallest laboratory reared larvae ascended into the upper portion of the column during the time of night and descended during the time of day. The other laboratory reared and field caught larvae had increased swimming activity during the time of night and reduced activity during the time of day. This circadian activity rhythm would contribute to the nocturnal DVM in offshore and estuarine areas. However, there was no evidence that larvae developed a tidal rhythm in activity that could contribute to selective tidal stream transport in estuaries.

Photoresponses of larval Atlantic menhaden ( Brevoortia tyrannus Latrobe) in offshore and estuarine waters: implications for transport

This study tested the hypothesis that Atlantic menhaden ( Brevoortia tyrannus Latrobe) larvae have separate behaviors in offshore and estuarine waters that are evoked by chemical cues in these waters. Atlantic menhaden spawn offshore, and larvae are transported shoreward where they metamorphose after entering estuaries. Field studies suggest that during the day larvae are at moderate depths offshore and less abundant in the water column than at night in estuaries. Since photoresponse may contribute to these depth distributions, they were tested in the laboratory in a light field that mimicked the underwater angular light distribution. Responses were quantified as the proportion of larvae swimming in the upper portion of a water column containing either offshore or estuarine water at the same salinity and temperature. Swimming varied significantly with water type. Young larvae (< 8 mm total length (TL)) swam near the surface in estuarine water and lower in offshore water. Older larvae (14–16 mm TL) showed the opposite responses. Since the test waters only differed in chemical composition, the results supported the hypothesis. In addition, the study characterized the predator avoidance shadow response, in which larvae descend in response to a decrease in light intensity. The shadow response did not change with larval age and was very similar in offshore and estuarine water. The minimum percent decrease in light intensity to evoke the descent response ranged from 37–50%. Young larvae descended primarily by passive sinking. Older larvae sank upon small decreases in intensity, but actively swam down in response to large intensity decreases. Thus, water type induced positional changes in a water column which may reflect the vertical position necessary for horizontal transport in offshore and estuarine areas by different age larvae. In contrast, the shadow response remained consistent, which suggests the predator threat is the same in offshore and estuarine areas and does not change with larval age.

Evidence for enhanced salinity tolerance of a suspected fungal pathogen of Atlantic menhaden, Brevoortia tyrannus Latrobe

Abstract. Two saprolegniaceous fungi, one recovered from Atlantic menhaden, Brevoortia tyrannus Latrobe, and the other from fresh water, were compared for their abilities to withstand salinity stress. Results of stress protein analyses indicated that vegetative mycelium of the isolate from menhaden was better adapted to mesohaline salinities than the freshwater isolate. Experiments testing the propagative ability of both fungi during salt exposure further suggested that the fungus recovered from menhaden was more salt tolerant and possibly survives in estuaries because of nutrients present in susceptible fish. Implications of the findings relative to the pathogenic potential of fish pathogenic saprolegniaceous fungi in estuarinc water columns are discussed.

Toxicity of Ozonated estuarine water to juvenile blue crabs (Callinectes sapidus) and Juvenile Atlantic menhaden (Brevoortia tyrannus).

Large quantitites of estuarine and marine water are treated with chlorine to prevent condenser system fouling at power plants. Chlorine and its residual by-products, however, are toxic to many forms of aquatic life. Ozone is one alternative oxidant which has proven to be an effective biocide and disinfectant in many fresh water applications. Ozonation of estuarine and marine waters, however, may produce residual compounds similar to those produced by chlorination. This study was initiated to provide baseline information on the toxicity of ozonated estuarine water to two representative estuarine species. The blue crab, Callinectes sapidus Rathbun, and the Atlantic menhaden, Brevoortia tyrannus Latrobe, were selected because of their wide distribution and commercial importance. The toxicity of ozone has been compared with chlorine toxicity data from the literature in an effort to examine possible similarities in toxicity.