Relationships among long'term fisheries abundances, hydrographic variables, and gross pollution indicators in northeastern U.S. estuaries

Abstract

Categorical time series regression was applied to 55 fish stocks in the Potomac, Hudson, Narragansett, Delaware, and Connecticut estuaries for the period 1929–1975. Interannual variability in catch per unit effort (CPUE) was related to CPUE, hydrographic variables, and pollution variables, lagged back in time to represent the conditions contributing to the multiple ages comprising each fishery. Hydrographic variables included water temperature and flow in the estuary– and, for offshore spawning stocks, wind direction and magnitude–during the months of spawning and early life stage development. Pollution variables included measures of dissolved oxygen conditions in the estuaries, volume of material dredged, and sewage loading (or human population). Lagged CPUE, hydrographic variables, and pollution variables all played important roles in explaining historical variability in CPUE. Lagged CPUE was significant in 45 of 55 stocks generally accounting for 5–35% of the variability. Lagged hydrographic variables were significant in 53 of 55 stocks, explaining an additional 5–40% of the variability unaccounted for by lagged CPUE. Lagged pollution variables were significant in 35 of 55 stocks, generally accounting for an additional 5–30% of the variability not explained by lagged CPUE and hydrographic variables. Results did not exhibit expected patterns of consistency in the importance of lagged CPUE for a species across estuaries or consistency in the importance of pollution variables across estuaries. Results did exhibit the expected north‐to‐south longitudinal pattern in the importance of timing of the hydrographic variables, the months of importance being one or two months later in more northerly estuaries. Higher‐order interaction effects were important in almost all stocks that were well‐modeled by categorical time series regression. Of the 30 stocks with final regression models having R2 > 0.55, 26 stocks involved significant interaction effects, five had only significant interaction effects (no significant main effects), and 20 stocks had significant interactions involving variables not significant as main effects. The difficulties involved in analyzing long‐term trends in fish populations and partitioning variability between natural and anthropogenic sources are discussed.

Interactive effects of abiotic, hydrological and anthropogenic factors on fish abundance and distribution in natural run‐of‐the‐river shallow lakes

“…Interactive effects from environmental factors are important contributors to interannual variation in the abundances of estuarine fish stocks (Rose and Summers, 1992). Salinity by its own was reported as a structuring factor in some inland 'freshwater' ecosystems (Echelle et al, 1972;Miquelarena and López, 1995).…”

Is the Response of Estuarine Nekton to Freshwater Flow in the San Francisco Estuary Explained by Variation in Habitat Volume?

“…Positive flow effects have been reported for phytoplankton production (Riley 1937;Mallin et al 1993;Sin et al 1999) and for abundance or harvest of benthic invertebrates (Aleem 1972;Gammelsrød 1992;Montagna and Kalke 1992;Wilber 1992Wilber , 1994Reaugh et al 2007) and fish (Stevens 1977;Houde and Rutherford 1993;Jassby et al 1995). Negative effects on biological populations can also occur (Rose and Summers 1992), e.g., through effects of washout or osmotic stress (Deegan 1990;Kaartvedt and Aksnes 1992).…”

Why are Quantitative Relationships between Environmental Quality and Fish Populations so Elusive?

“…This variability often appears as "noise" to investigators and resource managers, making the measurement and detection of the effects of individual factors difficult. Rose and Summers (1992) showed how interactive effects among environmental factors were important contributors to interannual variation in the abundances of estuarine fish stocks. Thus, for example, the effects on population size of changes in temperature during months of spawning differed depending on the magnitude of freshwater flow.…”

“…Often, much of the variation in abundance results from variability in hydrographic and climate-related variables that affect the very sensitive prerecruit life stages (Shepard et al 1984, Rose and Summers 1992, Laevastu 1993. Freshwater fish populations also exhibit large variations in recruitment and abundance, with biological interactions probably playing more of a role in the postlarval life stages that are less sensitive to environmental conditions (Houde 1994).…”