The ornamental fish trade involves transporting live specimens for several days, during which the fish are in starvation conditions and water quality may change in detrimental of the fish. Therefore, packing method, fish density and transit time are important issues affecting the trade activity and representing major cost for traders. We evaluated the effect of transportation time (24 or 48 hours) and fish density (1, 3 or 4 fish/packing unit) on the water quality and biological performance in juvenile long snout seahorse Hippocampus reidi.
Seahorses were kept without food 24h before packing. Juvenile seahorses (average 7.6 cm SL and 0.90 gr wet weight) were packed in 1-L plastic bags filled with 400 ml of filtered seawater at the commercial farm “INGENS Cultivos Marinos” in Mazatlán, Mexico. Four threads of raffia were placed inside each bag as a holdfast for the seahorses. A total of 24 bags were used, six bags per fish density (1, 3, 4 fish/bag) and six bags with no fish that were treated in the same way as control. After packing, bags with seahorses and controls were placed inside a closed styrofoam box (12.5” H x 25” L x 15.5” W) and shipped in the morning via air cargo from Mazatlán, México to La Paz, BCS, Mexico. Transit time was 24 hrs. After arrival to the laboratory at La Paz (24H), a total of 12 bags (3 per density and 3 controls) were removed from the box and used for the analysis and the other 12 bags were kept in the box for analysis at the next day (48H). We evaluated the fish survival after 24H of arrival. We also analyzed the change in water quality (temperature, pH, salinity, ammonia, dissolves oxygen, nitrates and nitrites) in each bag. Seahorses were measured and weighted to evaluate the condition factor. Protein concentration was also evaluated. The swimming activity and feeding intensity during 5 mins was evaluated when each seahorse was transferred from the transport bag to a 20L aquarium filled with filtered and UV sterilized seawater at the same temperature of the transportation bag.
Survival at arrival to the lab and after 48H was 100%. Nevertheless, water quality was significantly affected by transit time and fish density, particularly the ammonia concentration, fluctuating from 0.0 to 6.7 mg/L and the dissolved oxygen concentration from 10.2 to 6.0 mg/L. Transit time or packing density had no effect (p > 0.05) on the condition factor of the seahorses (average k = 0.20). However, the protein concentration of the juveniles was affected, but only significantly (p < 0.05) by the transit time (24H = 1.63 mg/ml, 48H = 1.57 mg/ml). The behavior analysis and feeding response showed that a 48H transit time had a significant effect on seahorses’ activity. The feeding intensity was significantly higher (p < 0.05) in the seahorses of the 48H treatment (4.6 prey/seahorse) than in the 24H treatment (2.1 prey/seahorse). The packing density had no significant effect on feeding intensity (p > 0.05). The results suggest that 3 or 4 seahorses/bag is an adequate packing density and that up to 48H of transit time had no significant effect on survival or welfare of the juveniles.