Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- Water cortisol and testosterone in Nile tilapia (Oreochromis niloticus) recirculating aquaculture systemsPublication . Mota, Vasco; Martins, Catarina I. M.; Eding, Ep H.; Canario, Adelino; Verreth, Johan A. J.The accumulation of steroids released by fish in recirculating aquaculture systems (RAS) may potentially influence their physiology and behavior. The present study examined the release rate of cortisol and testosterone by Nile tilapia, Oreochromis niloticus, and their accumulation in six identical lab scale RAS operated at different water exchange rates (150 L/kg feed/day, (LowRAS) and 1500 L/kg feed/day, (HighRAS)) and how steroid accumulation is affected by grading and weighing induced stress. Water cortisol and testosterone concentrations during the experimental period ranged between 1.0 and 5.1 ng/L and between 1.4 and 9.4 ng/L, respectively. Water cortisol concentration was 34% and 43% significantly higher in LowRAS when compared with HighRAS at week 3 and week 4, whereas for water testosterone concentration the two treatments did not differ. Overall steroid release rates were 0.02 +/- 0.02 and 0.04 +/- 0.02 ng/g body weight/h for cortisol and testosterone, respectively. Two hours after grading and weighing water cortisol concentration increased 30% in the LowRAS whereas water testosterone concentration remained unchanged. Calculated cortisol and testosterone discharge from the system were, respectively, 87% and 89% lower in LowRAS than in HighRAS. These findings show that reduced water usage and acute stressors can induce significant accumulation of cortisol in the rearing water at levels close to olfactory detection. Accumulation of metabolites, in particular steroids, should be taken in consideration when designing and managing RAS to prevent exceeding allowable concentrations. Statement of relevance: RAS containing Nile tilapia, cortisol and testosterone are released to the culture water. Water cortisol concentration depends on the water exchange rate that is used and higher concentrations are expected in lower water exchange rates. Fish grading and weighing has a short-term effect on the water cortisol concentrations, after which concentrations return to the basal levels. These findings show that reduction in water usage and fish handling may lead to a significant increase of hormones in the rearing water, which emphasizes the importance of accounting for steroids in the design and management of RAS. (C) 2016 Elsevier B.V. All rights reserved.
- Effects of low pH and high TA-N on performance of turbot (Psetta maxima) in recirculating aquaculture systemsPublication . Mota, Vasco; Heinsbroek, Johan; Sampaio, Luís AndréTurbot (Psetta maxima) is an emerging species in aquaculture, with a great expansion potential. Recirculating aquaculture systems (RAS) for this species are being developed in several countries. Under this intensive fish farming conditions stress is frequent. In this report primary, secondary, and tertiary stress responses were studied in turbot (374 ± 4 g) exposed during 59 days to low pH (5.8) alone or in combination with high NH4 +‐N concentration (50 mg. L‐1 NH4 +‐N), plus a control (pH 7.5 and <1 mg. L‐1 NH4 +‐N) in duplicate RAS. At the end of the chronic exposure there were no significant differences in plasma cortisol and glucose levels. Survival was also similar for all groups. However, turbot reared at low pH and high ammonium showed blood acidosis and significantly higher Na+ and Cl‐ plasmatic concentrations. These fish also showed a significantly lower growth rate compared to the control. After the growth trial, turbot were submitted to an acute stressor, where fish were chased with a dip net for 5 min and air exposed for additional 10 min. Blood was collected immediately before the stress induction and after 2 and 24 h. The stress response after 2 h involved activation of the HPI‐axis in a similar way to turbot in all groups, as indicated by the cortisol elevations coupled with higher glucose and lactate levels. An iono‐osmorregulatory misbalance was also observed after 2 h, as demonstrated by higher osmolality, Na+ and Cl‐ concentrations. Acid‐base disturbances were also observed, there was a visible drop of blood pH and HCO3 ‐ concentration. After 24 h, the above parameters for turbot in the control group returned to resting levels. However, fish exposed to a previous chronic stressor still presented altered values for osmolality, ionic, and acid‐base parameters. Turbot exposure to low pH in combination with high ammonium concentration showed disturbances at homeostasis level and a reduced feed intake, which lead to a lower growth rate. Low pH alone did not hamper the fish growth rate. However, after an additional acute stressor, turbot reared at low pH alone revealed a longer recovery time at hydro‐mineral and acid‐base balance than fish in the control group. The effect of this misbalance should be further investigated in order to assess the feasibility of keeping turbot at low pH for long periods.
- Steroids accumulate in the rearing water of commercial recirculating aquaculture systemsPublication . Mota, Vasco; Martins, Catarina I. M.; Eding, Ep; Canario, Adelino V. M.; Verreth, JohanLittle information is available on steroid concentrations in the rearing water of aquaculture systemsand whether they accumulate in recirculating aquaculture systems (RAS). Therefore this study aimedat determining (1) the concentrations and variation of cortisol and sex steroids in RAS, (2) the con-tribution of fish rearing conditions to steroid concentrations in seven commercial RAS. Each RAS wassampled twice at three different points: (1) make-up water; (2) influent and (3) effluent of the rear-ing unit. The results showed significant higher steroid concentrations in the influent and effluent whencompared with the make-up water. On average cortisol concentration was 15.7% higher in the efflu-ent when compared with the influent. Mean steroid concentrations in the rearing unit effluent variedbetween: 3.8–217.0 ng/L for cortisol, 3–12.5 ng/L for testosterone, 0.9–7.1 ng/L for 11-ketoteststerone and1.8–12.8 ng/L for 17,20 -dihydroxypregn-4-en-3-one. Stocking density, Total Ammonia-Nitrogen con-centration and orthophosphate-P concentration (a measure of make-up water usage) showed a positivecorrelation with sex steroids in the water. The steroid concentrations from the present study were ordersof magnitude lower than initial estimations indicating a water treatment efficiency of >99%. The resultssuggest that an intensification of fish production through decrease of make-up water use and increaseof stocking density will lead to a build-up of steroids in the water. Although intensification is critical forthe economical success of RAS, this ultimately could affect fish performance as steroids accumulates inthe water of RAS at levels that can potentially be detected by some fish species.
- Chemical communication in tilapia: a comparison of Oreochromis mossambicus with O. niloticusPublication . Hubbard, Peter; Mota, Vasco; Keller-Costa, Tina; Silva, José P. da; Canario, Adelino V. M.In allopatric speciation species differentiation generally results from different selective pressures in different environments, and identifying the traits responsible helps to understand the isolation mechanism(s) involved. Male Mozambique tilapia (Oreochromis mossambicus) use urine to signal dominance; furthermore, 5-pregnane-3,17,20-triol-3-glucuronide (and its -epimer, 5-pregnane-3,17,20-triol-3-glucuronide), in their urine is a potent pheromone, the concentration of which is correlated with social status. The Nile tilapia (O. niloticus) is a close relative; species divergence probably resulted from geographical separation around 6 million years ago. This raises the question of whether the two species use similar urinary chemical cues during reproduction. The olfactory potency of urine, and crude extracts, from either species was assessed by the electro-olfactogram and the presence of the steroid glucuronides in urine from the Nile tilapia by liquid-chromatography/mass spectrometry. Both species showed similar olfactory sensitivity to urine and respective extracts from either species, and similar sensitivity to the steroid glucuronides. 5-pregnan-3,17,20-triol-3-glucuronide was present at high concentrations (approaching 0.5 mM) in urine from Nile tilapia, with 5-pregnan-3,17,20-triol-3-glucuronide present at lower concentrations, similar to the Mozambique tilapia. Both species also had similar olfactory sensitivity to estradiol-3-glucuronide, a putative urinary cue from females. Together, these results support the idea that reproductive chemical cues have not been subjected to differing selective pressure. Whether these chemical cues have the same physiological and behavioural roles in O. niloticus as O. mossambicus remains to be investigated.
- Cortisol and testosterone accumulation in a low pH recirculating aquaculture system for rainbow trout (Oncorhynchus mykiss)Publication . Mota, Vasco; Martins, Catarina I. M.; Eding, Ep H.; Canario, Adelino V. M.; Verreth, Johan A. J.Steroids accumulate in recirculating aquaculture system (RAS), although explanatory factors for such accumulation are still poorly explored. This study investigated the effect of water exchange rate and pH in six replicated RAS on the concentration of the stress hormone cortisol in rainbow trout blood plasma and in the holding water and of the sex steroids testosterone, 11-ketotestosterone (11-KT) and 17,20-dihydroxypregn-4-en-3-one (17,20-P) over a 70-day experimental period. Three combinations of water exchange rate and pH were used each treatment, with two replications: (i) high water exchange rate (+/- 1700Lkg(-1) feed) and neutral pH (+/- 7.3), (ii) low water exchange rate (+/- 500Lkg(-1) feed) and neutral pH (+/- 7.3) and (iii) low water exchange rate (+/- 500Lkg(-1) feed) and low pH (+/- 5.8). Plasma cortisol concentrations at day 70 were higher (24.4 +/- 9.5ngmL(-1)) for fish kept at low pH when compared to fish kept at neutral pH (12.0 +/- 0.1 and 8.7 +/- 0.2ngmL(-1)). Water cortisol and testosterone concentrations at day 35 were higher at low pH than at neutral pH, whereas water 11-KT and 17,20-P did not differ among treatments. At day 70, there were no significant differences between low and high pH. These results demonstrate that low pH contributes to increased plasma cortisol concentrations and to its accumulation in water, possibly indicating a stress response to low pH. The higher concentration of testosterone but not of the other sex hormones point to unspecified reproductive effects that need further investigation.