Sea Lice on Salmon: Sampling Process:
In sampling juvenile salmon, we have used a nonlethal sampling procedure developed for the Raincoast Research Society that significantly reduces analyze the methodology costs, mortality. The method may also be used to determine fish health. Samples are analyzed on site. The method is applicable to monitoring programs of juvenile pink salmon, chum salmon, or both during their nearshore life history phase and provides a nonlethal alternative to study depressed or threatened populations. The simplicity of the protocol facilitates public participation in sampling programs, and public interest exists in many coastal communities.
British Columbia wild juvenile pink and chum salmons are threatened. Both species share a unique life history among anadromous salmonids: juveniles emerge from gravel and immediately enter the marine environment. This makes them the smallest salmonids to contend with marine parasites. They rear in nearshore habitats during their seaward migration typically in mixed schools. Juvenile pink and chum salmons are captured with a beach seine off rocky intertidal shorelines. The minimum recommended dimensions of the seine net are 20 x 1.5 m with 4-mm mesh size for salmon with a less than 5.5 cm fork length, and 35 x 3 m with 4-mm mesh for salmon 5.5– 10 cm. Upon capture, live samples are stored in buckets where appropriate water temperature and dissolved oxygen levels are maintained. Stress to fish was minimized during transfer to buckets both to protect fish health and to minimize louse loss. Juvenile salmon were analyzed on site. Individual fish were placed inside a clear plastic envelope without water for analysis. A sufficient envelope is a standard large ziplock storage bag (3.7 L, 27 x 28 cm) with the top portion of the bag cut and removed to create a 27 x 12-cm envelope. The position of the fish is controlled by the surface tension of the envelope and all surfaces and fins of the fish were viewed. A hand lens is sufficient to differentiate copepodid, chalimus, and motile stages. It was difficult to distinguish the two louse species with this technique for most parasitic stages except gravid females, which is when obvious morphological differences emerge. However, since both species exist on salmon, they were grouped and assayed together, as has been practiced in other studies. Fish health observations were recorded (hemorrhaging, scarring, predation marks, lesions, and fin erosion) and were not confounded by sacrificing and freezing specimens as occur in traditional methods. After analysis, fish were allowed to recover and then released at the location of capture.
Cate McEwan, Bob Sharp, Alain Dalaire and Kevin O'Connor took part in the juvenile salmon census in which ES classes examined all netted fish, looking for sea lice on the salmon.
In sampling juvenile salmon, we have used a nonlethal sampling procedure developed for the Raincoast Research Society that significantly reduces analyze the methodology costs, mortality. The method may also be used to determine fish health. Samples are analyzed on site. The method is applicable to monitoring programs of juvenile pink salmon, chum salmon, or both during their nearshore life history phase and provides a nonlethal alternative to study depressed or threatened populations. The simplicity of the protocol facilitates public participation in sampling programs, and public interest exists in many coastal communities.
British Columbia wild juvenile pink and chum salmons are threatened. Both species share a unique life history among anadromous salmonids: juveniles emerge from gravel and immediately enter the marine environment. This makes them the smallest salmonids to contend with marine parasites. They rear in nearshore habitats during their seaward migration typically in mixed schools. Juvenile pink and chum salmons are captured with a beach seine off rocky intertidal shorelines. The minimum recommended dimensions of the seine net are 20 x 1.5 m with 4-mm mesh size for salmon with a less than 5.5 cm fork length, and 35 x 3 m with 4-mm mesh for salmon 5.5– 10 cm. Upon capture, live samples are stored in buckets where appropriate water temperature and dissolved oxygen levels are maintained. Stress to fish was minimized during transfer to buckets both to protect fish health and to minimize louse loss. Juvenile salmon were analyzed on site. Individual fish were placed inside a clear plastic envelope without water for analysis. A sufficient envelope is a standard large ziplock storage bag (3.7 L, 27 x 28 cm) with the top portion of the bag cut and removed to create a 27 x 12-cm envelope. The position of the fish is controlled by the surface tension of the envelope and all surfaces and fins of the fish were viewed. A hand lens is sufficient to differentiate copepodid, chalimus, and motile stages. It was difficult to distinguish the two louse species with this technique for most parasitic stages except gravid females, which is when obvious morphological differences emerge. However, since both species exist on salmon, they were grouped and assayed together, as has been practiced in other studies. Fish health observations were recorded (hemorrhaging, scarring, predation marks, lesions, and fin erosion) and were not confounded by sacrificing and freezing specimens as occur in traditional methods. After analysis, fish were allowed to recover and then released at the location of capture.
Cate McEwan, Bob Sharp, Alain Dalaire and Kevin O'Connor took part in the juvenile salmon census in which ES classes examined all netted fish, looking for sea lice on the salmon.