Biology and fishery of the 'Titi' shrimp Xiphopenaeus Riveti on the Pacific Coast of Colombia, South America

Mora-Lara, Carlos Orlando (1973) Biology and fishery of the 'Titi' shrimp Xiphopenaeus Riveti on the Pacific Coast of Colombia, South America. Masters thesis, Memorial University of Newfoundland.

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Abstract

The commercial importance of this species in Colombia is reflected in landings of about four million pounds (tail weight) in 1971, having been increasingly reported in the last few years as demand and price increased. Analysis of the fishery indicated the necessity for management by limiting the number of vessels before depletion would become apparent. Biology of the species, based on monthly samples taken during survey fishing, gave conversion factors of 1.62 for tail weight to total weight and 0.61 for total weight to tail weight. Length-weight, etc., relationships indicated that males gained more weight with increase in size than females, but the latter grew to much larger sizes. Maxima for carapace length were 26 and 35mm, respectively, in the samples. Average monthly growth in females was estimated at 2.9 mm carapace length. First maturity in males was reached at a carapace length of 15 mm; maturity was continuous thereafter, as shown by presence of spermatophores. In females, first maturity was observed at 17 mm cl, but data on their reproductive cycles indicates that they mature and spawn up to four times over the period indicated by the range of carapace length observed. Their gonads were rated as juvenile, immature, maturing, and mature, based on sizes of ovaries and ova, the largest ova being 0.25 mm in diameter before spawning. High percentages with large ova in each monthly sample indicated frequent spawnings, probably numbering five times a year for the population. -- Procercoids of cestodes parasitized principally the hepatopancreas. Food organisms were observed to be primarily other crustaceans, polychaetes and pelecypods. The sex ratio was biased in favour of females. This is interpreted to be due to a gear selection or preference of/for larger shrimp. With regards to bathymetric distribution, 5-10 m and mostly in near-shore locations were favoured, and some adults, as well as juveniles, were found within estuaries. Recruitment appeared to occur four times annually, based on length frequency samples. -- The thesis further examines the taxonomy of the genus and the species and morphology details of X. riveti are given. However, no final decision is made concerning the separation of X. riveti and X. kroyeri.

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