Measuring marine fish biodiversity: temporal changes in abundance, life history and demography

• Published in: Philosophical Transactions of the Royal Society B: Biological Sciences
• Main Authors: Hutchings, Jeffrey A, Baum, Julia K
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2005
• Subjects: Pacific; atlantic cod; Gadus morhua; Northeast Atlantic; Northwest Atlantic
• Online Access: http://dx.doi.org/10.1098/rstb.2004.1586; https://royalsocietypublishing.org/doi/pdf/10.1098/rstb.2004.1586; https://royalsocietypublishing.org/doi/full-xml/10.1098/rstb.2004.1586

Patterns in marine fish biodiversity can be assessed by quantifying temporal variation in rate of population change, abundance, life history and demography concomitant with long-term reductions in abundance. Based on data for 177 populations (62 species) from four north-temperate oceanic regions (Northeast Atlantic and Pacific, Northwest Atlantic, North mid-Atlantic), 81% of the populations in decline prior to 1992 experienced reductions in their rate of loss thereafter; species whose rate of population decline accelerated after 1992 were predominantly top predators such as Atlantic cod ( Gadus morhua ), sole ( Solea solea ) and pelagic sharks. Combining population data across regions and species, marine fish have declined 35% since 1978 and are currently less than 70% of recorded maxima; demersal species are generally at historic lows, pelagic species are generally stable or increasing in abundance. Declines by demersal species have been associated with substantive increases in pelagic species, a pattern consistent with the hypothesis that increases in the latter may be attributable to reduced predation mortality. There is a need to determine the consequences to population growth effected by the reductions in age (21%) and size (13%) at maturity and in mean age (5%) and size (18%) of spawners, concomitant with population decline. We conclude that reductions in the rate of population decline, in the absence of targets for population increase, will be insufficient to effect a recovery of marine fish biodiversity, and that great care must be exercised when interpreting multi-species patterns in abundance. Of fundamental importance is the need to explain the geographical, species-specific and habitat biases that pervade patterns of marine fish recovery and biodiversity.