A historical review of the shad fisheries of North America

A review of the relative productivity and value of the shad fisheries of North America as reflected in recorded commercial catches. A review of reasons for the decline that are biological and socioeconomic. Factors that have been held responsible are: pollution; destruction or impairment of spawning and nursery areas; overfishing; hydroelectric and canal dams; natural fluctuations in abundance. Natural catastrophes, parasites, and predators are not considered important in causing the decrease in commercial production. Attempts to rehabilitate the fisheries by various means of stocking artificially-reared fry and pond-reared fingerling shad, appear to have failed in every instance. Introduction of shad fry on the Pacific Coast has resulted in a major fishery. The most significant program is a controlled catch management plan, operating at this time [1953] only in Maryland.

The role of substrate, flow and larval supply to recruitment of the red abalone (Haliotis rufescens)

Precipitous declines in wild populations of the red abalone Haliotis rufescens and the eventual closure of the commercial and southern recreational fishery have led to renewed interest in supplementing wild stocks with hatchery-raised individuals. Most work to date has focused on releasing small juveniles and has had limited success. Although much is known about larval settlement, juvenile survivorship and growth of abalone, there is scanty information on natural processes in the field. The failure of many regulated fisheries worldwide suggests that both the larval and juvenile stages may be important in determining the future population, and that early juvenile mortality is more important than previously believed. This paper presents a series of experiments designed to examine factors and mechanisms that could affect settlement, survivorship, and growth of larvae and early post-settlers in the field. Laboratory trials under different flow regimes showed that red abalone larvae settled preferentially on substrates encrusted with coralline algae, and that settlement was rapid when exposed to crusts compared to other surfaces. Urchin grazing of films appeared to facilitate abalone settlement but only when urchins were removed. Initial field experiments showed that released larvae settled on natural cobble rock, and that settlement was at least one order of magnitude greater when settlement habitats were tented. I then examined post-settlement survivorship at one and two days after settlement, and found that although there was a large amount of variation, on average 10% of released larvae were found as newly-settled recruits after 1 day. Survivorship and growth of recruits were followed over at least one month in both Spring and Fall. Abalone settled at higher densities, survived better and grew faster in the warmer Fall months than in the Spring. The density of month-old abalone recruits was correlated with density of naturally-occurring gastropods in the Spring, but not in the Fall. These results suggest that settlement and survivorship can be extremely variable across space and time, and that oceanographic and local biotic conditions play a role and should be considered when planning larval seeding.