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Population structure, growth and production of a recent brachiopod from the C hilean fjord region
Author(s) -
Baumgarten Sebastian,
Laudien Jürgen,
Jantzen Carin,
Häussermann Verena,
Försterra Günter
Publication year - 2014
Publication title -
marine ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.668
H-Index - 58
eISSN - 1439-0485
pISSN - 0173-9565
DOI - 10.1111/maec.12097
Subject(s) - fjord , population , benthic zone , zoology , juvenile , growth rate , biology , fishery , ecology , oceanography , geology , mathematics , demography , geometry , sociology
Magellania venosa, the largest recent brachiopod, occurs in clusters and banks in population densities of up to 416 ind m −2 in Comau Fjord, Northern Chilean fjord region. Below 15 m, it co‐occurs with the mytilid A ulacomya atra and it dominates the benthic community below 20 m. To determine the question of why M . venosa is a successful competitor, the in situ growth rate of the brachiopod was studied and its overall growth performance compared with that of other brachiopods and mussels. The growth in length was measured between February 2011 and March 2012 after mechanical tagging and calcein staining. Settlement and juvenile growth were determined from recruitment tiles installed in 2009 and from subsequent photocensus. Growth of M . venosa is best described by the general von Bertalanffy growth function, with a maximum shell length ( L ∞ ) of 71.53 mm and a Brody growth constant ( K ) of 0.336 year −1 . The overall growth performance (OGP index = 5.1) is the highest recorded for a rynchonelliform brachiopod and in the range of that for M ytilus chilensis (4.8–5.27), but lower than that of A. atra (5.74). The maximal individual production ( P Ind ) is 0.29 g AFDM ind −1 year −1 at 42 mm shell length and annual production ranges from 1.28 to 89.25 g AFDM year −1 m −2 (1–57% of that of A. atra in the respective fjords). The high shell growth rate of M . venosa, together with its high overall growth performance may explain the locally high population density of this brachiopod in Comau Fjord. However, the production per biomass of the population ( P / B ¯‐ratio) is low (0.535) and M . venosa may play only a minor role in the food chain. Settling dynamics indicates that M . venosa is a pioneer species with low juvenile mortality. The coexistence of the brachiopod and bivalve suggests that brachiopod survival is affected by neither the presence of potential brachiopod predators nor that of space competitors ( i.e . mytilids).