A proposal for sea otter protection and research and request for the return of management to the State of California

v.1 - Text and Summaries (272 page document)

Earth Systems: the foundation of Florida’s Ecosystems

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Analysis of fish diversion efficiency and survivorship in the fish return system at San Onofre Nuclear Generating Station

This study examined the efficiency of fish diversion and survivorship of diverted fishes in the San Onofre Nuclear Generating Station Fish Return System in 1984 and 1985. Generally, fishes were diverted back to the ocean with high frequency, particularly in 1984. Most species were diverted at rates of 80% or more. Over 90% of the most abundant species, Engraulis mordax, were diverted. The system worked particularly well for strong-swimming forms such as Paralobrax clothratus, Atherinopsis californiensis, and Xenistius californiensis, and did not appreciably divert weaker-swimming species such as Porichthys notatus, Heterostichus rostratus, and Syngnathus sp. Return rates of some species were not as high in 1985 as in 1984. Individuals of most tested species survived both transit through the fish return system and 96 hours in a holding net. Some species, such as E. mordox, X. californiensis, and Umbrina roncador, experienced tittle or no mortality. Survivorship of Seriphus politus was highly variable and no Anchoa delicatissima survived. (PDF file contains 22 pages.)

Down to earth thoughts on conserving aquatic genetic diversity

A discussion is presented on the topic of maintaining genetic diversity in aquatic ecosystems, considering the various threats caused by irreversible damage or loss to the environment. The current situation in aquaculture and future prospects regarding the conservation and protection of endangered species are outlined, describing the case of tilapias in Africa as one particular example of fish conservation.

Estimating long-term growth-rate changes of southern bluefin tuna (Thunnus maccoyii) from two periods of tag-return data

Southern bluefin tuna (SBT) (Thunnus maccoyii) growth rates are estimated from tag-return data associated with two time periods, the 1960s and 1980s. The traditional von Bertalanffy growth model (VBG) and a two-phase VBG model were fitted to the data by maximum likelihood. The traditional VBG model did not provide an adequate representation of growth in SBT, and the two-phase VBG yielded a significantly better fit. The results indicated that significant change occurs in the pattern of growth in relation to a VBG curve during the juvenile stages of the SBT life cycle, which may be related to the transition from a tightly schooling fish that spends substantial time in near and surface shore waters to one that is found primarily in more offshore and deeper waters. The results suggest that more complex growth models should be considered for other tunas and for other species that show a marked change in habitat use with age. The likelihood surface for the two-phase VBG model was found to be bimodal and some implications of this are investigated. Significant and substantial differences were found in the growth for fish spawned in the 1960s and in the 1980s, such that after age four there is a difference of about one year in the expected age of a fish of similar length which persists over the size range for which meaningful recapture data are available. This difference may be a density-dependent response as a consequence of the marked reduction in the SBT population. Given the key role that estimates of growth have in most stock assessments, the results indicate that there is a need both for the regular monitoring of growth rates and for provisions for changes in growth over time (possibly related to changes in abundance) in the stock assessment models used for SBT and other species.

Some effects of Earth's surface on winter jet stream positions in the Northern Hemisphere and rainfall patterns in northern and central California

EXTRACT (SEE PDF FOR FULL ABSTRACT): This report shows that the mean wintertime polar-front jet stream structure consists of three long waves. Prominent ridges in the jet stream flow occur near the longitudes of India, eastern Pacific/west coast of North America, and eastern Atlantic/British Isles; prominent troughs occur near the longitudes of the Middle East, western Pacific, and western Atlantic/east coast of North America. ... One of the climatological ridges occurs along the west coast of North America ... just off the central Oregon coast. The position of the jet stream at this location appears to be the main reason most Pacific storms pass to the north of California. Sustained rainfall in northern and central California occurs only when the storm track is displaced southward of this climatological position.

Production and economic return in pangasiid catfish (Pangasius hypophthalmus) monoculture and polyculture with silver carp (Hypophthalmichthys molitrix) in farmers' ponds

The production of fish and net economic return in pangasiid catfish (Pangasius hypophthalmus) monoculture and polyculture with silver carp (Hypophthalmichthys molitrix) in farmers' ponds were assessed. The experiment was arranged in three treatments each with three replications. The ponds were stocked with 30,000 fishes per hectare. In treatment 1 (T1) pangasiid catfish only, in treatment 2 (T2) pangasiid catfish and silver carp at the ratio of 1:1, and in treatment 3 (T3) pangasiid catfish and silver carp at the ratio of 2:1 were stocked. At harvest, production of fish was found significantly (p<0.05) different among the treatments, highest in T1 and lowest in T2. Though the total biomass production and total economic return was significantly highest in T1 than in T2 and T3, the net economic return was lowest because of the required highest input costs especially for supplemental feed and fingerlings, resulted the highest cost per unit yield (CPY in Tk/kg) in T1. Highest cost for supplemental feed required in T1 was due to highest quantity of feed required for the highest number of pangasiid catfish stocked in that treatment. The findings of the present study suggest that though monoculture of pangasiid catfish give higher fish biomass production but polyculture with silver carp is environmentally good and economically profitable.