title: Boat electrofishing survey of the Awatapu Lagoon and lower Tarawera River

authors: Hicks, Brendan J.

abstract: The Department of Conservation (DOC) and Bay of Plenty Regional Council contracted the University of Waikato to conduct a boat electrofishing survey of the Awatapu Lagoon, the old Rangitaiki River channel and the lower Tarawera River. This survey was in response to sightings of large orange fish at these sites by members of the public and the consequent concern that these fish might be koi carp (Cyprinus carpio; Pete Livingstone, DOC, Whakatane). We also recorded species of native fish to determine their relative density and biomass.  
We fished the Awatapu Lagoon in October 2005 and December 2014, and we fished the old Rangitaiki River channel and the lower Tarawera River in December 2014. In the Awatapu Lagoon on 31 October 2005, we caught 260 fish, comprising 170 goldfish weighing a total of 27.5 kg, 88 shortfin eels (Anguilla australis), and two brown trout. In addition, common smelt (Retropinna retropinna), inanga (Galaxias maculatus) and gambusia (Gambusia affinis) were abundant, though their numbers were not quantitatively determined. The two adult brown trout we caught measured 450 and 460 mm fork length (FL), giving calculated weights of approximately 1.21 and 1.29 kg. Mean goldfish density was 1.70 fish 100 m⁻², with individuals ranging in size from 40 to 277 mm (FL) (mean FL 178 mm ± 42 mm standard deviation, SD). Mean weight of 162 g (± 97 g SD), and mean goldfish areal biomass was 1.70 g m⁻². Shortfin eel density was estimated as 1.87 fish 100 m⁻² in East Lagoon, but biomass was not estimated for shortfin eels. Eels were seen in West Lagoon but not caught. No koi carp or other invasive fish species were found. 
In December 2014, we caught 271 fish comprising 12 species (two introduced, and 10 native). Common bullies (Gobiomorphus cotidianus) and shortfin eels were the most numerous species. In the Awatapu Lagoon, we caught 102 common bullies, 64 goldfish and 22 shortfin eels. In the lower Tarawera River, we caught parore (Girella tricuspidata), a stargazer (Leptoscopus macropygus), and yelloweye mullet (Aldrichetta forsteri). Site T4 in the Tarawera River had the greatest species richness (7 species). We verified that the large orange cyprinids that were seen in the old Rangitaiki River channel were large goldfish and not koi carp.  
As the main purpose of this fishing was to establish the identity of large orange fish seen in and round the lower Tarawera and the Awatapu Lagoon, the occurrence of goldfish was significant. From the size and colour ranges and abundance of the goldfish caught it is highly likely that any orange fish seen were large orange goldfish and not koi carp. However, before this fishing it was quite reasonable to conclude that large orange fish might be koi carp. This is similar to the Kaituna River, where goldfish were found but there were no koi carp. The high diversity of native fish species in the lower  Tarawera  River  is  predictable  from  known  fish  distribution  patterns,  where  the  most  diverse fish communities are found close to the coast. The occurrence of parore is unusual in freshwater fishing, as these are generally considered to be a marine species, but do stray into estuaries. One giant bully was found in this survey, and these are quite common in the lower reaches of large river systems. Yelloweye mullet are also common in Bay of Plenty fresh waters close to the sea.  Stargazers are a relatively unusual catch, but we have found these previously in Bay of Plenty rivers and in the lower Manawatu River.

text: Boat electrofishing survey of the Awatapu Lagoon and lower Tarawera River The Department of Conservation (DOC) and Bay of Plenty Regional Council contracted the University of Waikato to conduct a boat electrofishing survey of the Awatapu Lagoon, the old Rangitaiki River channel and the lower Tarawera River. This survey was in response to sightings of large orange fish at these sites by members of the public and the consequent concern that these fish might be koi carp (Cyprinus carpio; Pete Livingstone, DOC, Whakatane). We also recorded species of native fish to determine their relative density and biomass.  
We fished the Awatapu Lagoon in October 2005 and December 2014, and we fished the old Rangitaiki River channel and the lower Tarawera River in December 2014. In the Awatapu Lagoon on 31 October 2005, we caught 260 fish, comprising 170 goldfish weighing a total of 27.5 kg, 88 shortfin eels (Anguilla australis), and two brown trout. In addition, common smelt (Retropinna retropinna), inanga (Galaxias maculatus) and gambusia (Gambusia affinis) were abundant, though their numbers were not quantitatively determined. The two adult brown trout we caught measured 450 and 460 mm fork length (FL), giving calculated weights of approximately 1.21 and 1.29 kg. Mean goldfish density was 1.70 fish 100 m⁻², with individuals ranging in size from 40 to 277 mm (FL) (mean FL 178 mm ± 42 mm standard deviation, SD). Mean weight of 162 g (± 97 g SD), and mean goldfish areal biomass was 1.70 g m⁻². Shortfin eel density was estimated as 1.87 fish 100 m⁻² in East Lagoon, but biomass was not estimated for shortfin eels. Eels were seen in West Lagoon but not caught. No koi carp or other invasive fish species were found. 
In December 2014, we caught 271 fish comprising 12 species (two introduced, and 10 native). Common bullies (Gobiomorphus cotidianus) and shortfin eels were the most numerous species. In the Awatapu Lagoon, we caught 102 common bullies, 64 goldfish and 22 shortfin eels. In the lower Tarawera River, we caught parore (Girella tricuspidata), a stargazer (Leptoscopus macropygus), and yelloweye mullet (Aldrichetta forsteri). Site T4 in the Tarawera River had the greatest species richness (7 species). We verified that the large orange cyprinids that were seen in the old Rangitaiki River channel were large goldfish and not koi carp.  
As the main purpose of this fishing was to establish the identity of large orange fish seen in and round the lower Tarawera and the Awatapu Lagoon, the occurrence of goldfish was significant. From the size and colour ranges and abundance of the goldfish caught it is highly likely that any orange fish seen were large orange goldfish and not koi carp. However, before this fishing it was quite reasonable to conclude that large orange fish might be koi carp. This is similar to the Kaituna River, where goldfish were found but there were no koi carp. The high diversity of native fish species in the lower  Tarawera  River  is  predictable  from  known  fish  distribution  patterns,  where  the  most  diverse fish communities are found close to the coast. The occurrence of parore is unusual in freshwater fishing, as these are generally considered to be a marine species, but do stray into estuaries. One giant bully was found in this survey, and these are quite common in the lower reaches of large river systems. Yelloweye mullet are also common in Bay of Plenty fresh waters close to the sea.  Stargazers are a relatively unusual catch, but we have found these previously in Bay of Plenty rivers and in the lower Manawatu River.

year: 2015

title: Biophysical, environmental, and economic implications of removing imported supplementary feed from a pasture-based dairy farm system -An upper North Island case study

authors: McCahon, Kieran Shaun

subjects: milk production

abstract: The biological efficiency and profitability of pasture-based systems is optimised by matching pasture supply with the nutritional demands of the herd across the year. Despite the importance of grazed pasture to the profitability of pasture-based systems, the use of purchased (i.e., non-pasture) feeds (supplementary feeds) has increased considerably over the last two decades within the New Zealand (NZ) dairy industry. 
Supplementary feeds may be offered to maintain or increase dry matter intake (DMI) and milk production during periods when pasture supply is insufficient to meet herd demands (i.e., a pasture deficit). However, published results indicate that, despite greater milk production and gross farm revenue (GFR), imported supplementary feed is not associated with an increase in profitability. In addition, the intensification of grazing systems through concurrent increases in stocking rate (SR) have been associated with poorer environmental outcomes, such as reduced water quality and increased greenhouse gas (GHG) emissions. 
The primary objective of my Masters project was to investigate the biophysical, economic, and environmental effects of removing imported supplementary feed from a typical pasture-based system in the upper North Island of New Zealand. This was conducted over three years in Northland, New Zealand (35⁰56’39”S 173⁰50’34”E), using a quantitative case-study approach that compared three pasture-based dairy farming treatments differing in SR and the nature of feed supply. As a Control treatment, imported supplementary feed was offered as palm kernel expeller (PKE) during periods of pasture deficit (~ 550kg DM/cow/yr; ~ 10% of the cows’ diet; PKE treatment). This was compared with two alternative systems to remove the need for PKE: 1) reduced SR (Pasture treatment); or, 2) growing potentially high yielding forage crops on the dairy platform and maintaining SR (Cropping treatment). I used the nutrient budgeting software OVERSEER to model treatment effects on nitrogen (N) leaching, phosphorous (P) loss, and GHG emissions. In addition, I conducted a Monte Carlo analysis to investigate economic performance of all three treatments and how it varied over a range of key input prices.
On average, despite no significant difference in milk production, operating profit tended to be lower in the Cropping treatment relative to the PKE treatment. In addition, after accounting for variability in market prices, the Cropping treatment returned a lower operating profit at every probability level relative to the PKE treatment and was, therefore, an inferior system for a profit-focused decision maker.
Milk production and associated GFR were lower in the Pasture treatment compared with the PKE treatment; however, there was no effect of treatment on operating profit at average market prices. When accounting for potential market price variability, the PKE treatment returned a greater operating profit in 70% of scenarios. As a result, the PKE treatment would likely provide a preferable system for a profit-focused decision maker, with low to moderate risk aversion. However, the relative profitability of treatments was highly dependent on the marginal milk production response (MMPR) to supplementary feed. Consistently large MMPRs to supplementary feed were achieved in the current study: 30 to 50% greater than published farm systems experiments. A reduction in the MMPR to supplementary feed by 10% eroded the profit advantage of the PKE treatment. In addition, despite no treatment effect on N leaching, GHG emissions tended to be lower in the Pasture treatment relative to the PKE treatment. As a result, a decision maker, paying or receiving incentives to reduce environmental externalities would likely be indifferent between the PKE and Pasture treatments, even with the large MMPR to supplementary feed achieved in the current study. Depending on the potential response to supplementary feed, profitability may be maintained with the removal of imported supplementary feeds from a pasture-based system by decreasing SR.

text: Biophysical, environmental, and economic implications of removing imported supplementary feed from a pasture-based dairy farm system -An upper North Island case study The biological efficiency and profitability of pasture-based systems is optimised by matching pasture supply with the nutritional demands of the herd across the year. Despite the importance of grazed pasture to the profitability of pasture-based systems, the use of purchased (i.e., non-pasture) feeds (supplementary feeds) has increased considerably over the last two decades within the New Zealand (NZ) dairy industry. 
Supplementary feeds may be offered to maintain or increase dry matter intake (DMI) and milk production during periods when pasture supply is insufficient to meet herd demands (i.e., a pasture deficit). However, published results indicate that, despite greater milk production and gross farm revenue (GFR), imported supplementary feed is not associated with an increase in profitability. In addition, the intensification of grazing systems through concurrent increases in stocking rate (SR) have been associated with poorer environmental outcomes, such as reduced water quality and increased greenhouse gas (GHG) emissions. 
The primary objective of my Masters project was to investigate the biophysical, economic, and environmental effects of removing imported supplementary feed from a typical pasture-based system in the upper North Island of New Zealand. This was conducted over three years in Northland, New Zealand (35⁰56’39”S 173⁰50’34”E), using a quantitative case-study approach that compared three pasture-based dairy farming treatments differing in SR and the nature of feed supply. As a Control treatment, imported supplementary feed was offered as palm kernel expeller (PKE) during periods of pasture deficit (~ 550kg DM/cow/yr; ~ 10% of the cows’ diet; PKE treatment). This was compared with two alternative systems to remove the need for PKE: 1) reduced SR (Pasture treatment); or, 2) growing potentially high yielding forage crops on the dairy platform and maintaining SR (Cropping treatment). I used the nutrient budgeting software OVERSEER to model treatment effects on nitrogen (N) leaching, phosphorous (P) loss, and GHG emissions. In addition, I conducted a Monte Carlo analysis to investigate economic performance of all three treatments and how it varied over a range of key input prices.
On average, despite no significant difference in milk production, operating profit tended to be lower in the Cropping treatment relative to the PKE treatment. In addition, after accounting for variability in market prices, the Cropping treatment returned a lower operating profit at every probability level relative to the PKE treatment and was, therefore, an inferior system for a profit-focused decision maker.
Milk production and associated GFR were lower in the Pasture treatment compared with the PKE treatment; however, there was no effect of treatment on operating profit at average market prices. When accounting for potential market price variability, the PKE treatment returned a greater operating profit in 70% of scenarios. As a result, the PKE treatment would likely provide a preferable system for a profit-focused decision maker, with low to moderate risk aversion. However, the relative profitability of treatments was highly dependent on the marginal milk production response (MMPR) to supplementary feed. Consistently large MMPRs to supplementary feed were achieved in the current study: 30 to 50% greater than published farm systems experiments. A reduction in the MMPR to supplementary feed by 10% eroded the profit advantage of the PKE treatment. In addition, despite no treatment effect on N leaching, GHG emissions tended to be lower in the Pasture treatment relative to the PKE treatment. As a result, a decision maker, paying or receiving incentives to reduce environmental externalities would likely be indifferent between the PKE and Pasture treatments, even with the large MMPR to supplementary feed achieved in the current study. Depending on the potential response to supplementary feed, profitability may be maintained with the removal of imported supplementary feeds from a pasture-based system by decreasing SR.

year: 2019

title: Matariki: The star of the year by Rangi Matamua [Book Review]

authors: Keegan, Te Taka Adrian Gregory

abstract: This article reviews the book “Matariki: The star of the year by Rangi Matamua", by Matamua, Rangi.

text: Matariki: The star of the year by Rangi Matamua [Book Review] This article reviews the book “Matariki: The star of the year by Rangi Matamua", by Matamua, Rangi.

year: 2017