The Northwest Atlantic deep-sea red crab (Chaceon quinquedens) population before and after the onset of harvesting

Abstract

Wahle, R. A., Bergeron, C. E., Chute, A. S., Jacobson, L. D., and Chen, Y. 2008. The Northwest Atlantic deep-sea red crab (Chaceon quinquedens) population before and after the onset of harvesting. – ICES Journal of Marine Science, 65: 862–872. The population structure of deep-sea red crab (Chaceon quinquedens) in a nearly unexploited state is compared with its condition three decades later after more than a decade of sustained harvesting. Our study is based on a camera and net trawl survey conducted in 1974, which we repeated between 2003 and 2005 on the southern New England shelf break. Although the overall biomass of red crabs was estimated to be higher than in 1974, the abundance of large males, which are targeted by the fishery, was considerably lower. In particular, the biomass of large males (≥114 mm carapace width), considered in 1974 to be marketable, declined by 42%. Declines were most evident at depths and regions most accessible to the fishing fleet based in southern New England. With the change in fishery selectivity towards smaller male crabs, the abundance of currently harvestable crabs is about equal to 1974 levels. No declines were observed in the biomass of female and smaller male crabs not targeted by the fishery. Indeed, the abundance of juveniles appears considerably higher than in 1974. Perhaps, adverse effects on reproduction attributable to a reduction in the numbers of large males may be a consequence of fishing, but fishery impacts and productivity are difficult to assess because key biological information is lacking.

Sexual maturity of the deep sea red crab Chaceon notialis Manning & Holthuis, 1989 (Brachyura: Geryonidae) in southern Brazil

“…Delgado & Defeo (2004) suggested that, due to the selective exploitation of males, the sperm supply might have become a limiting resource for the population. A similar concern was raised by Wahle et al (2008) for the northwest Atlantic red crab C. quinquedens fishery, where the abundance of large males declined by 42% after three decades of selective harvesting. Our results could support the Delgado & Defeo (2004) hypothesis, considering that most C. notialis males caught in Brazil (supposedly in much lower numbers than in the original population structure) have shown signs of reproductive activity (copula marks), but a proportionally smaller portion of the females seem to have been effectively fertilized.…”

Depth and temperature distribution, morphometrics, and sex ratios of red deepsea crab (Chaceon quinquedens) at 4 sampling sites in the Mid-Atlantic Bight

“…Density of crab was calculated as the catch (total number) of each sex divided by the area towed and expressed as the mean number of crab·per hectare, for comparison with results reported by Wahle et al (2008). Because replicate tows were not made at each station, density of each sex was compared separately between years, sites, and depth strata by using single-factor analysis of variance (ANOVA), and P-values <0.05 were considered significant.…”

“…The red deepsea crab (Chaceon quinquedens) ranges from the Gulf of Maine to the Gulf of Mexico, at depths from 200 to 1800 m, and temperatures of 5-8°C (Haefner and Musick, 1974;Wigley et al, 1975; Serchuk 1 ; Steimle et al, 2001;Wahle et al, 2008;NEFSC 2 ). Stocks along the Atlantic coast are considered a single population and distinct from the stock in the Gulf of Mexico.…”

“…Stocks along the Atlantic coast are considered a single population and distinct from the stock in the Gulf of Mexico. Red deepsea crab support a small but valuable fishery in federally managed waters along the continental slope of southern New England and the Mid-Atlantic, a fishery that has been managed since 2002 by the New England Fishery Management Council (Wigley et al, 1975;Wahle et al, 2008). In recent years, 4 vessels have fished for red deepsea crab and have averaged annual landings of 1360 metric tons (t) over the time period 2002-2013, but landings have declined from 1600 to 930 t during that period (Chute 3 ).…”

“…The first survey (Wigley et al, 1975) was conducted in 1974 before the onset of commercial fishing. The second, conducted during 2003-2005(Wahle et al, 2008, showed a 250% increase in overall biomass (mostly due to juveniles), after a decade of targeted harvesting of males, but a 42% decline in the biomass of large males at depths of 350-500 m where fishing occurs, as well as a decline in body condition indices (carapace length [CL]: weight ratios) (Weinberg and Keith, 2003). In addition, the size of landed crabs has declined from 114 mm in carapace width (CW) in 1974 to <90 mm CW by 2008 (Chute et al 4 ).…”