1,721,058 research outputs found
Submission to UN Ocean Conference 2022 for Interactive Dialogue: Managing, protecting, conserving and restoring marine and coastal ecosystems
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Fertilization kinetics in marine invertebrates
No full textAllee (1931) first reported that reproductive success in free-spawning marine invertebrates was dependent on population density. However, little attention was paid to the 'Allee' effect until Pennington's (1985) pivotal paper describing the consequences of sperm dilution in echinoid fertilization. This thesis is a study of the factors affecting fertilization success in five species of commercial shellfish. Commercial shellfish are particularly prone to the deleterious 'Allee' effect. These shellfish are subject to natural and anthropogenic disturbances and disease, and certain species have been severely over-exploited. Some shellfisheries have declined to such an extent that natural recovery is almost impossible (Roberts and Hawkins, 1999).This thesis examined pre-larval effects on reproductive success in terms of fertilization kinetics. A series of laboratory experiments were conducted to determine fertilization success in the abalone, Haliotis tuberculata; the oyster, Crassostrea gigas; the clam, Tapes decussatus; the limpet, Patella vulgata and the echinoid, Psammechinus miliaris. For all of these species, fertilization success was found to be reliant upon a number of factors such as sperm dilution, gamete age, sperm-egg ratio, sperm-egg contact time and temperature. These data indicate that sperm limitation severely compromises reproductive success in commercially exploited populations of all these species.The laboratory-derived data were used with models of sperm dispersal and field experiments to determine minimum stocking densities that would be required to support successful recruitment in adult populations, in an attempt to combat the 'Allee' effect.</p
The deep ocean - a new stewardship frontier
No full textTechnological advances in recent decades underpin the massive progress in the exploration and characterization of deep-sea ecosystems, revealing highly diverse deep-sea floor habitats and a realm that is vulnerable to disturbance. Nonetheless, the deep sea remains mostly unknown. Likewise, gaps in governance abound as most legal frameworks, both national and international, lack essential mechanisms to manage and protect ocean resources such as provisions for integrated, ecosystem-based and systematic planning and management. A significant challenge here is that management needs to keep pace with fast-growing industries. This communication focuses on three main aspects of the legacy of Professor Mario Ruivo for sustainable use of the deep oceans 1) scientific discovery and observation; 2) legal and policy tools; and 3) awareness and global environmental justice
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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