How has the average diet of striped bass changed over the years?
**Striped bass (*Morone saxatilis*) are opportunistic predators with highly flexible diets that vary by life stage (ontogeny), season, region, habitat, and prey availability.** Their diet has shown notable shifts over decades in key areas like the Chesapeake Bay, San Francisco Estuary, Hudson River, and Massachusetts estuaries, driven by changes in forage abundance, environmental factors (e.g., invasions, water quality), and striped bass population recovery. (LINK)
### General Patterns in Striped Bass Diet
– **Young-of-the-year (YOY) and juveniles**: Primarily invertebrates (zooplankton, copepods, mysids, amphipods, isopods, shrimp, worms) and some small fish as they grow. They shift toward more piscivory (fish-eating) above ~50 mm TL. (LINK)
– **Subadults and adults**: Shift to larger prey like schooling fish (e.g., menhaden, anchovies, herring), with invertebrates (crabs, shrimp) remaining important depending on location and season.
– Diets reflect local availability: pelagic schooling fish dominate in many areas, but benthic invertebrates or other fish increase where those are abundant. (LINK)
### Key Changes Over Time
**Chesapeake Bay (most studied area, major spawning/nursery ground)**:
– **1950s (historical baseline)**: Atlantic menhaden (*Brevoortia tyrannus*) dominated, especially for larger fish (high IRI). Bay anchovy (*Anchoa mitchilli*) was secondary, more for smaller bass. Invertebrates like blue crabs were minor. (LINK)
– **1990s–2000s (post-recovery period)**: Shift toward more bay anchovy and invertebrates (e.g., blue crabs, mysids, polychaetes). Menhaden consumption dropped significantly (e.g., age-1/2 bass ate 11–15x less menhaden than in the 1950s). Larger bass relied more on small pelagic prey like anchovies (16–29% by weight in some seasons). Blue crabs became more prominent. (LINK)
– Reasons: Declines in menhaden abundance, striped bass population recovery (increasing predation pressure), and seasonal/habitat shifts. Overall energy consumption may have decreased in some age classes despite adaptability. (LINK)
**San Francisco Estuary / Sacramento-San Joaquin Delta**:
– **1960s vs. 2000s**: Evidence of trophic adaptability—striped bass incorporated new/invasive prey (e.g., threadfin shad, Siberian prawn) quickly. However, mysid shrimp (historical dominant for young bass) declined sharply, contributing to lower carrying capacity and young bass abundance despite switches to other invertebrates and fish. (LINK)
**Hudson River**:
– Multi-decade studies (including zebra mussel invasion impacts) showed increased prey diversity initially, then shifts toward more benthic feeding. No major negative effect on overall feeding success from the invasion, but diets adjusted (e.g., more benthic prey). Copepods, amphipods, mysids, and *Leptodora* remained important. (LINK)
**Massachusetts / New England**:
– Recent shifts noted: From menhaden (late 1990s/early 2000s) toward Atlantic mackerel in some studies. Larger bass increasingly targeting benthic decapods (crustaceans) for energetic benefits, especially later in seasonal residency. Seasonal patterns strong (e.g., herring in spring, menhaden in fall). (LINK)
**Broader Atlantic Coast**:
– High variability: Over 65 fish species and 45+ invertebrates documented. Regional differences persist (e.g., more menhaden/anchovies in mid-Atlantic/south; more invertebrates or herring northward). Seasonal migrations influence prey (e.g., herring, peanut bunker). (LINK)
### Drivers of Change
– **Prey availability**: Declines in key forage (menhaden, mysids) due to overfishing, habitat changes, or invasions force switches.
– **Striped bass population dynamics**: Recovery from 1980s lows increased competition and predation pressure.
– **Environmental factors**: Warming waters, eutrophication, invasives (e.g., zebra mussels), and altered energy flow in estuaries.
– **Ontogeny and adaptability**: Bass switch prey effectively on short (seasonal) to long (decadal) scales, but full replacement of high-quality historical prey isn’t always possible, potentially affecting growth/condition. (LINK)
Overall, striped bass remain generalists capable of adapting, but long-term shifts often reflect broader ecosystem changes rather than preference alone. Data is strongest for Chesapeake Bay; other regions show similar flexibility with local nuances. For the latest or site-specific details, targeted studies or monitoring programs are ideal.