title: Assessment of injury to New Zealand native fish by boat electrofishing

authors: de Villiers, Joshua

subjects: Electrofishing

abstract: This study investigated the survival, incidence and severity of injuries and physiological reactions to stress caused by boat electrofishing in comparison with standard netting techniques in three New Zealand native fish species. Shortfin eel (Anguilla australis), grey mullet (Mugil cephalus) and common smelt (Retropinna retropinna) were captured from the Waikato River and its surrounding lakes with standardised boat electrofishing techniques (60-Hz pulsed direct current, 45-60% of range with the 0-500-V peak voltage machine setting, 3-4 Amps root mean square output). Fish were captured in water of 133-154 μScm─1 ambient conductivity at 18-21oC. Capture techniques used for comparison were fyke netting for eels, gill netting for grey mullet and beach seine netting for smelt.
Survival was assessed in eels that held for 30 days after capture and smelt that were held for 30 min after capture. Several different methods were used to assess the incidence and severity of injuries. External examinations were used to assess branding and abrasions, and internal injuries were assessed by radiographic imaging and bilateral filleting to reveal haemorrhaging and spinal damage. Finally, physiological stress was determined by an analysis of haematocrit and haemoglobin concentration and an analysis of blood plasma ions (sodium, potassium, magnesium and calcium).
Survival over 30 days of shortfin eels captured by electrofishing (92% for Lake Areare eels and 96% for Lake Rotongaro eels) was similar to that for fyke netting (92% for Lake Areare and 88% for Lake Rotongaro). Two eels appeared to have died from fungal infections as no haemorrhaging or spinal injuries were apparent among the mortalities. External examinations revealed that no abrasions or branding occurred in eels captured by electrofishing; however, abrasions occurred in eels captured by fyke netting (24% for Lake Areare eels and 16% for Lake Rotongaro eels).
Rates of internal haemorrhaging immediately after electrofishing were inconsistent (0% in Lake Areare and 28% in Lake Rotongaro); in Lake Rotongaro, this was significantly greater than those captured by fyke netting, in which only 8% had haemorrhages. No haemorrhaging was observed in eels after 30 days from Lake Areare. Haemorrhages from electrofishing in our study appeared to heal within the 30-day holding period, as the incidence of haemorrhaging in Rotongaro eels reduced from 28% at capture to only 4% after 30 days in captivity. Rates of spinal injury in eels captured by electrofishing was also variable (12% in Lake Areare eels and 8% in Lake Rotongaro eels), compared to the rate of spinal injury in eels captured by fyke netting (0% in Lake Areare eels and 4% in Lake Rotongaro eels). The upper rate of haemorrhaging that we found for electrofishing in shortfin eels (28%) was similar to injury rates for electrofished American eels (25%), but our rates of spinal damage (8-12%) were much lower than for American eels (60%).
In grey mullet, there was no significant difference (P > 0.101) in the occurrence of haemorrhages or spinal injuries between the two capture methods. However, physiological stress from electrofishing caused a significantly (t = 2.37, P = 0.02) reduced sodium ion concentration (139.38 ± 13.24 mM) compared to that of gill netting (149.06 ± 15.58 mM). Electrofishing also caused a significantly (t = 4.61, P < 0.001) lower concentration of haemoglobin (86.55 ± 9.21 g L-1) compared to that of grey mullet captured by gill netting (108.81 ± 23.86 g L-1). However, there were no significant differences between capture methods for the other blood plasma constituents tested (haematocrit and the blood plasma ions sodium, potassium, magnesium and calcium).
Survival was high in smelt captured by both electrofishing (94.8%, n = 1217) and by seine netting (92.9%, n = 1271), with no statistically significant difference between the two fishing methods (t = −1.021, P = 0.320). In a subsample of smelt analysed for injuries (n = 40 for each method), external injuries were observed in 15% (n = 6) of smelt captured by electrofishing and in 20% (n = 8) of smelt captured by seine netting. No haemorrhages were detected in smelt for either of the capture methods and there was no significant difference (G = 0.215, P = 0.642) in the rate of spinal injuries in smelt captured by electrofishing (10%, n = 4) or by seine netting (5%, n = 2).
These results suggest that boat electrofishing as practiced in New Zealand is in the long term generally no more harmful to shortfin eels, grey mullet, and common smelt than other comparable capture sampling techniques. Exceptions to this
conclusion were increased haemorrhaging in electrofished shortfin eels, from which they recovered within 30 days, and reduced sodium and haemoglobin concentrations in electrofished grey mullet, which are signs of physiological stress. All fishing methods examined caused some level of injury, stress, or mortality in the three species studied. Netting techniques (fyke net, gill netting, and seine netting) that are commonly used will also cause harm and these techniques are currently used far more widely than boat electrofishing.

text: Assessment of injury to New Zealand native fish by boat electrofishing This study investigated the survival, incidence and severity of injuries and physiological reactions to stress caused by boat electrofishing in comparison with standard netting techniques in three New Zealand native fish species. Shortfin eel (Anguilla australis), grey mullet (Mugil cephalus) and common smelt (Retropinna retropinna) were captured from the Waikato River and its surrounding lakes with standardised boat electrofishing techniques (60-Hz pulsed direct current, 45-60% of range with the 0-500-V peak voltage machine setting, 3-4 Amps root mean square output). Fish were captured in water of 133-154 μScm─1 ambient conductivity at 18-21oC. Capture techniques used for comparison were fyke netting for eels, gill netting for grey mullet and beach seine netting for smelt.
Survival was assessed in eels that held for 30 days after capture and smelt that were held for 30 min after capture. Several different methods were used to assess the incidence and severity of injuries. External examinations were used to assess branding and abrasions, and internal injuries were assessed by radiographic imaging and bilateral filleting to reveal haemorrhaging and spinal damage. Finally, physiological stress was determined by an analysis of haematocrit and haemoglobin concentration and an analysis of blood plasma ions (sodium, potassium, magnesium and calcium).
Survival over 30 days of shortfin eels captured by electrofishing (92% for Lake Areare eels and 96% for Lake Rotongaro eels) was similar to that for fyke netting (92% for Lake Areare and 88% for Lake Rotongaro). Two eels appeared to have died from fungal infections as no haemorrhaging or spinal injuries were apparent among the mortalities. External examinations revealed that no abrasions or branding occurred in eels captured by electrofishing; however, abrasions occurred in eels captured by fyke netting (24% for Lake Areare eels and 16% for Lake Rotongaro eels).
Rates of internal haemorrhaging immediately after electrofishing were inconsistent (0% in Lake Areare and 28% in Lake Rotongaro); in Lake Rotongaro, this was significantly greater than those captured by fyke netting, in which only 8% had haemorrhages. No haemorrhaging was observed in eels after 30 days from Lake Areare. Haemorrhages from electrofishing in our study appeared to heal within the 30-day holding period, as the incidence of haemorrhaging in Rotongaro eels reduced from 28% at capture to only 4% after 30 days in captivity. Rates of spinal injury in eels captured by electrofishing was also variable (12% in Lake Areare eels and 8% in Lake Rotongaro eels), compared to the rate of spinal injury in eels captured by fyke netting (0% in Lake Areare eels and 4% in Lake Rotongaro eels). The upper rate of haemorrhaging that we found for electrofishing in shortfin eels (28%) was similar to injury rates for electrofished American eels (25%), but our rates of spinal damage (8-12%) were much lower than for American eels (60%).
In grey mullet, there was no significant difference (P > 0.101) in the occurrence of haemorrhages or spinal injuries between the two capture methods. However, physiological stress from electrofishing caused a significantly (t = 2.37, P = 0.02) reduced sodium ion concentration (139.38 ± 13.24 mM) compared to that of gill netting (149.06 ± 15.58 mM). Electrofishing also caused a significantly (t = 4.61, P < 0.001) lower concentration of haemoglobin (86.55 ± 9.21 g L-1) compared to that of grey mullet captured by gill netting (108.81 ± 23.86 g L-1). However, there were no significant differences between capture methods for the other blood plasma constituents tested (haematocrit and the blood plasma ions sodium, potassium, magnesium and calcium).
Survival was high in smelt captured by both electrofishing (94.8%, n = 1217) and by seine netting (92.9%, n = 1271), with no statistically significant difference between the two fishing methods (t = −1.021, P = 0.320). In a subsample of smelt analysed for injuries (n = 40 for each method), external injuries were observed in 15% (n = 6) of smelt captured by electrofishing and in 20% (n = 8) of smelt captured by seine netting. No haemorrhages were detected in smelt for either of the capture methods and there was no significant difference (G = 0.215, P = 0.642) in the rate of spinal injuries in smelt captured by electrofishing (10%, n = 4) or by seine netting (5%, n = 2).
These results suggest that boat electrofishing as practiced in New Zealand is in the long term generally no more harmful to shortfin eels, grey mullet, and common smelt than other comparable capture sampling techniques. Exceptions to this
conclusion were increased haemorrhaging in electrofished shortfin eels, from which they recovered within 30 days, and reduced sodium and haemoglobin concentrations in electrofished grey mullet, which are signs of physiological stress. All fishing methods examined caused some level of injury, stress, or mortality in the three species studied. Netting techniques (fyke net, gill netting, and seine netting) that are commonly used will also cause harm and these techniques are currently used far more widely than boat electrofishing.

year: 2013

title: Fate of allochthonous dissolved organic carbon in Lakes: A quantitative approach

authors: Hanson, Paul C.

abstract: Inputs of dissolved organic carbon (DOC) to lakes derived from the surrounding landscape can be stored, mineralized or passed to downstream ecosystems. The balance among these OC fates depends on a suite of physical, chemical, and biological processes within the lake, as well as the degree of recalcintrance of the allochthonous DOC load. The relative importance of these processes has not been well quantified due to the complex nature of lakes, as well as challenges in scaling DOC degradation experiments under controlled conditions to the whole lake scale. We used a coupled hydrodynamic-water quality model to simulate broad ranges in lake area and DOC, two characteristics important to processing allochthonous carbon through their influences on lake temperature, mixing depth and hydrology. We calibrated the model to four lakes from the North Temperate Lakes Long Term Ecological Research site, and simulated an additional 12 ‘hypothetical’ lakes to fill the gradients in lake size and DOC concentration. For each lake, we tested several mineralization rates (range: 0.001 d−1 to 0.010 d−1) representative of the range found in the literature. We found that mineralization rates at the ecosystem scale were roughly half the values from laboratory experiments, due to relatively cool water temperatures and other lake-specific factors that influence water temperature and hydrologic residence time. Results from simulations indicated that the fate of allochthonous DOC was controlled primarily by the mineralization rate and the hydrologic residence time. Lakes with residence times <1 year exported approximately 60% of the DOC, whereas lakes with residence times >6 years mineralized approximately 60% of the DOC. DOC fate in lakes can be determined with a few relatively easily measured factors, such as lake morphometry, residence time, and temperature, assuming we know the recalcitrance of the DOC.

text: Fate of allochthonous dissolved organic carbon in Lakes: A quantitative approach Inputs of dissolved organic carbon (DOC) to lakes derived from the surrounding landscape can be stored, mineralized or passed to downstream ecosystems. The balance among these OC fates depends on a suite of physical, chemical, and biological processes within the lake, as well as the degree of recalcintrance of the allochthonous DOC load. The relative importance of these processes has not been well quantified due to the complex nature of lakes, as well as challenges in scaling DOC degradation experiments under controlled conditions to the whole lake scale. We used a coupled hydrodynamic-water quality model to simulate broad ranges in lake area and DOC, two characteristics important to processing allochthonous carbon through their influences on lake temperature, mixing depth and hydrology. We calibrated the model to four lakes from the North Temperate Lakes Long Term Ecological Research site, and simulated an additional 12 ‘hypothetical’ lakes to fill the gradients in lake size and DOC concentration. For each lake, we tested several mineralization rates (range: 0.001 d−1 to 0.010 d−1) representative of the range found in the literature. We found that mineralization rates at the ecosystem scale were roughly half the values from laboratory experiments, due to relatively cool water temperatures and other lake-specific factors that influence water temperature and hydrologic residence time. Results from simulations indicated that the fate of allochthonous DOC was controlled primarily by the mineralization rate and the hydrologic residence time. Lakes with residence times <1 year exported approximately 60% of the DOC, whereas lakes with residence times >6 years mineralized approximately 60% of the DOC. DOC fate in lakes can be determined with a few relatively easily measured factors, such as lake morphometry, residence time, and temperature, assuming we know the recalcitrance of the DOC.

year: 2011

title: Colonial versus ancestral legacy: The assertion of culture and identity through public arts in Kirikiriroa/Hamilton

authors: Kiff, Shirin

subjects: Ethnography

abstract: This thesis is an ethnography of Hamilton. It focuses on the role of public arts as a cultural regeneration tool and their function in shaping the community(s) in Kirikiriroa/Hamilton through building a sense of place and identity. As a qualitative study, I conducted nine semi- structured interviews with public art artists, art advocates and residents to explore the relational context within which the development and transmission of meaning takes place, a process which is central to culture and identity. The primary purpose of the research interviews was to gain insight into the factors that motivate arts organisers and planners to direct valuable limited resources into public art projects and its observable outcomes. The second purpose of the interviews, conducted while walking to public artworks in the city centre with six participants, was to examine the effect of public art on the public.
My methods also include tracking press reviews, monitoring comments and posts on social media and institutional debates involving residents, artists, and public authorities concerning public arts. I also recorded data by taking photographs and recording field notes of my observations during and after the fieldwork process. Data gathering was also enhanced by the large-scale collection of written materials and resources, including public art publications and HCC policy documents. Taken together, these research methods allowed me to investigate whether Hamilton had achieved its goals in its cultural regeneration efforts. In my analysis, I discuss the role of public art and its association with place and consider how artworks may antagonise Māori-Pākehā relationships or otherwise emphasis residents’ sense of place.
Biculturalism and monoculturalism narratives appear to dominate public arts with the purpose of invoking either a colonial legacy or ancestral legacy while the politics of multiculturalism continue to jockey for place. Colonial legacy refers to the glorifying of colonial achievements while ancestral legacy in this context refers to Māori assertion of history, culture and identity. Particularly, in this research, ancestral legacy belonging to local hapū, Ngāti Wairere. Participants’ narratives reveal four overarching themes, 1) the publics’ resistance to the making of colonial places through public art, 2) Ngāti Wairere struggles to assert ancestral legacy through public arts, 3) the need for ethnically diverse artworks to create and maintain ethnically diverse places, and 4) a yearning for a collective identity represented through public arts. Hamilton’s public artworks are variously perceived as a superficial representation of Māori culture, identity and history, a reminder of a colonial binary discourse, the colonised versus the coloniser, an assertion of either a Māori ancestral legacy or a colonial legacy or, minimally, a nod to multiculturalism. Nevertheless, my research shows that participants engagement with these artworks reveal a yearning for a local collective identity that is still a work in progress.

text: Colonial versus ancestral legacy: The assertion of culture and identity through public arts in Kirikiriroa/Hamilton This thesis is an ethnography of Hamilton. It focuses on the role of public arts as a cultural regeneration tool and their function in shaping the community(s) in Kirikiriroa/Hamilton through building a sense of place and identity. As a qualitative study, I conducted nine semi- structured interviews with public art artists, art advocates and residents to explore the relational context within which the development and transmission of meaning takes place, a process which is central to culture and identity. The primary purpose of the research interviews was to gain insight into the factors that motivate arts organisers and planners to direct valuable limited resources into public art projects and its observable outcomes. The second purpose of the interviews, conducted while walking to public artworks in the city centre with six participants, was to examine the effect of public art on the public.
My methods also include tracking press reviews, monitoring comments and posts on social media and institutional debates involving residents, artists, and public authorities concerning public arts. I also recorded data by taking photographs and recording field notes of my observations during and after the fieldwork process. Data gathering was also enhanced by the large-scale collection of written materials and resources, including public art publications and HCC policy documents. Taken together, these research methods allowed me to investigate whether Hamilton had achieved its goals in its cultural regeneration efforts. In my analysis, I discuss the role of public art and its association with place and consider how artworks may antagonise Māori-Pākehā relationships or otherwise emphasis residents’ sense of place.
Biculturalism and monoculturalism narratives appear to dominate public arts with the purpose of invoking either a colonial legacy or ancestral legacy while the politics of multiculturalism continue to jockey for place. Colonial legacy refers to the glorifying of colonial achievements while ancestral legacy in this context refers to Māori assertion of history, culture and identity. Particularly, in this research, ancestral legacy belonging to local hapū, Ngāti Wairere. Participants’ narratives reveal four overarching themes, 1) the publics’ resistance to the making of colonial places through public art, 2) Ngāti Wairere struggles to assert ancestral legacy through public arts, 3) the need for ethnically diverse artworks to create and maintain ethnically diverse places, and 4) a yearning for a collective identity represented through public arts. Hamilton’s public artworks are variously perceived as a superficial representation of Māori culture, identity and history, a reminder of a colonial binary discourse, the colonised versus the coloniser, an assertion of either a Māori ancestral legacy or a colonial legacy or, minimally, a nod to multiculturalism. Nevertheless, my research shows that participants engagement with these artworks reveal a yearning for a local collective identity that is still a work in progress.

year: 2021