Carbon and nitrogen stable isotope values were determined in Pacific white shrimp (Litopenaeus vannamei) with the objective of discriminating animals produced through aquaculture practices from those extracted from the wild. Farmed animals were collected at semi-intensive shrimp farms in Mexico and Ecuador. Fisheries-derived shrimps were caught in different fishing areas representing two estuarine systems and four open sea locations in Mexico and Ecuador. Carbon and nitrogen stable isotope values (δ¹³C_VPDB and δ¹⁵N_AIR) allowed clear differentiation of wild from farmed animals. δ¹³C_VPDB and δ¹⁵N_AIR values in shrimps collected in the open sea were isotopically enriched (−16.99‰ and 11.57‰), indicating that these organisms belong to higher trophic levels than farmed animals. δ¹³C_VPDB and δ¹⁵N_AIR values of farmed animals (−19.72‰ and 7.85‰, respectively) partially overlapped with values measured in animals collected in estuaries (−18.46‰ and 5.38‰, respectively). Canonical discriminant analysis showed that when used separately and in conjunction, δ¹³C_VPDB and δ¹⁵N_AIR values were powerful discriminatory variables and demonstrate the viability of isotopic evaluations to distinguish wild-caught shrimps from aquaculture shrimps. Methodological improvements will define a verification tool to support shrimp traceability protocols.

Two feeding trials were carried out to evaluate the effect of diets containing corn or peanut grains naturally contaminated with aflatoxins on the growth, feed intake, survival, and histological response of the white shrimp Litopenaeus vannamei. In trial 1, four experimental diets were formulated to contain 0, 500, 1000, and 2000 µg kg–1 of total aflatoxins (TA) and fed to L. vannamei juveniles for 28 days. In trial 2, six experimental diets were formulated to contain 0, 10, 20, 40, 60, and 120 µg kg–1 TA and fed to L. vannamei juveniles for 64 days. Feed intake and weight gain were significantly affected by the presence of aflatoxins from naturally contaminated grains. Feed conversion rate increased significantly from a level of inclusion of 60 µg kg–1. Survival was significantly reduced only for shrimp fed diets supplemented with 1000 and 2000 µg kg–1 TA. Shrimp exposed to higher aflatoxin inclusion levels presented significantly lower lipid vacuole levels in R-cells (12–28%), lower B-cell activity, and lower mitotic E-cell activity. Tubular epithelial atrophy increased from the inclusion level of 20 µg kg–1. Hepatopancreatocyte sloughing was significantly higher in shrimp fed diets supplemented with 1000 and 2000 µg kg–1 TA. It is worth noting that shrimp fed 40 µg kg–1 TA presented a high hepatopancreatocyte sloughing coefficient. Based on these results we conclude that the presence of aflatoxins, even at low levels, reduces feed intake and weight gain, and alters the cells of the hepatopancreas.