Of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (Oncorhynchus gorbuscha)
Pink salmon (Oncorynchus gorbuscha) enter seawater (SW) following gravel emergence at a body mass of 0.2 g. Two hydromineral challenges associated with this remarkable early ocean entry were investigated: (1) initial exposure to a hyper-osmotic environment and (2) sea louse (Lepeophtheirus salmonis)...
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ftcanadathes:oai:collectionscanada.gc.ca:BVAU.2429/27218 2023-05-15T17:52:53+02:00 Of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (Oncorhynchus gorbuscha) Sackville, Michael 2010-08-09T20:24:08Z http://hdl.handle.net/2429/27218 eng eng University of British Columbia http://hdl.handle.net/2429/27218 http://creativecommons.org/licenses/by-nc-nd/3.0/ Attribution-NonCommercial 2.5 Canada CC-BY-NC-ND Electronic Thesis or Dissertation 2010 ftcanadathes 2014-03-30T00:45:55Z Pink salmon (Oncorynchus gorbuscha) enter seawater (SW) following gravel emergence at a body mass of 0.2 g. Two hydromineral challenges associated with this remarkable early ocean entry were investigated: (1) initial exposure to a hyper-osmotic environment and (2) sea louse (Lepeophtheirus salmonis) parasitism. To survive SW, pink salmon were hypothesized to develop hypo-osmoregulatory abilities as larval alevins prior to natural SW entry as post-larval fry. To test this, alevins and fry were transferred from freshwater (FW) in darkness to SW under a simulated natural photoperiod (SNP). Ionoregulatory status was assessed at 0, 1 and 5 days post-transfer. Alevins showed no evidence of hypo-osmoregulation, marked by a loss of water balance, a 35% increase in body [Cl-], and no change in gill Na⁺/K⁺-ATPase (NKA) activity. Conversely, fry maintained water balance and increased gill NKA activity by 50%. Fry gill NKA activity also increased by 50% following exposure to SNP in FW, providing the first evidence of photoperiod-triggered smoltification for pink salmon. A 15% increase in fry body [Na⁺] was observed as well, perhaps representing a novel mechanism for maintaining water balance during ocean entry. Physical damage to the host epidermis is a primary proximal effect of louse infection. Such damage may exacerbate existing hydromineral flux in SW. To test this, ionoregulatory status was measured in pink salmon of varying size with and without attached-stage lice. In laboratory-infected fish (~1 wk SW; 0.2-0.4 g), body [Na⁺] increased by 12% when infected with 1 chalimus IV louse, and by 23% with 2-3 chalimus III lice. Mortality was 6%. In wild-infected fish (~4-12 wks SW; 0.5-1.5 g), body [Na⁺] did not differ from controls. Combining data sets revealed a “no effect” fish size threshold of 0.5 g for 1 chalimus IV louse. This threshold is partly due to increasing hypo-osmoregulatory ability. Pink salmon thus appear to possess a novel hypo-osmoregulatory strategy where ion balance is sacrificed to maintain water balance prior to maximum ion excretion capacity. Out-migrating fish are particularly vulnerable to sea louse parasitism at this time, and as such, BC fish farms have relocated to minimize interactions during this critical period. Thesis Oncorhynchus gorbuscha Pink salmon Theses Canada/Thèses Canada (Library and Archives Canada) |
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Open Polar |
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Theses Canada/Thèses Canada (Library and Archives Canada) |
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ftcanadathes |
language |
English |
description |
Pink salmon (Oncorynchus gorbuscha) enter seawater (SW) following gravel emergence at a body mass of 0.2 g. Two hydromineral challenges associated with this remarkable early ocean entry were investigated: (1) initial exposure to a hyper-osmotic environment and (2) sea louse (Lepeophtheirus salmonis) parasitism. To survive SW, pink salmon were hypothesized to develop hypo-osmoregulatory abilities as larval alevins prior to natural SW entry as post-larval fry. To test this, alevins and fry were transferred from freshwater (FW) in darkness to SW under a simulated natural photoperiod (SNP). Ionoregulatory status was assessed at 0, 1 and 5 days post-transfer. Alevins showed no evidence of hypo-osmoregulation, marked by a loss of water balance, a 35% increase in body [Cl-], and no change in gill Na⁺/K⁺-ATPase (NKA) activity. Conversely, fry maintained water balance and increased gill NKA activity by 50%. Fry gill NKA activity also increased by 50% following exposure to SNP in FW, providing the first evidence of photoperiod-triggered smoltification for pink salmon. A 15% increase in fry body [Na⁺] was observed as well, perhaps representing a novel mechanism for maintaining water balance during ocean entry. Physical damage to the host epidermis is a primary proximal effect of louse infection. Such damage may exacerbate existing hydromineral flux in SW. To test this, ionoregulatory status was measured in pink salmon of varying size with and without attached-stage lice. In laboratory-infected fish (~1 wk SW; 0.2-0.4 g), body [Na⁺] increased by 12% when infected with 1 chalimus IV louse, and by 23% with 2-3 chalimus III lice. Mortality was 6%. In wild-infected fish (~4-12 wks SW; 0.5-1.5 g), body [Na⁺] did not differ from controls. Combining data sets revealed a “no effect” fish size threshold of 0.5 g for 1 chalimus IV louse. This threshold is partly due to increasing hypo-osmoregulatory ability. Pink salmon thus appear to possess a novel hypo-osmoregulatory strategy where ion balance is sacrificed to maintain water balance prior to maximum ion excretion capacity. Out-migrating fish are particularly vulnerable to sea louse parasitism at this time, and as such, BC fish farms have relocated to minimize interactions during this critical period. |
format |
Thesis |
author |
Sackville, Michael |
spellingShingle |
Sackville, Michael Of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (Oncorhynchus gorbuscha) |
author_facet |
Sackville, Michael |
author_sort |
Sackville, Michael |
title |
Of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (Oncorhynchus gorbuscha) |
title_short |
Of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (Oncorhynchus gorbuscha) |
title_full |
Of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (Oncorhynchus gorbuscha) |
title_fullStr |
Of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (Oncorhynchus gorbuscha) |
title_full_unstemmed |
Of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (Oncorhynchus gorbuscha) |
title_sort |
of saline and sea lice : hydromineral challenges and osmoregulatory strategies associated with early ocean entry of juvenile pink salmon (oncorhynchus gorbuscha) |
publisher |
University of British Columbia |
publishDate |
2010 |
url |
http://hdl.handle.net/2429/27218 |
genre |
Oncorhynchus gorbuscha Pink salmon |
genre_facet |
Oncorhynchus gorbuscha Pink salmon |
op_relation |
http://hdl.handle.net/2429/27218 |
op_rights |
http://creativecommons.org/licenses/by-nc-nd/3.0/ Attribution-NonCommercial 2.5 Canada |
op_rightsnorm |
CC-BY-NC-ND |
_version_ |
1766160640897974272 |