Broome boat ramp study indicates boating popularity

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Researchers have analysed a year’s worth of video imagery from the popular Entrance Point boat ramp, adjacent to the Broome Fishing Club, to explore the factors affecting the launching of recreational boats, as part of a broader WAMSI study looking at Human Use in the Kimberley.  

In total, 6057 recreational boat launches were recorded by the Western Australian Department of Fisheries camera at Entrance Point during the 12 month study. The figure shows that, despite the town of Broome only having a relatively small resident population of about 13,000 people, boating is a popular activity.

To put it into context, the total at Entrance Point is equivalent to about 22 per cent of the total number of launches per year at Hillarys boat ramp which is one of the busiest in the Perth Metropolitan area.

On a seasonal basis, 60 per cent of all boat launches at Entrance Point occurred during the dry, winter season (May to October) and on a monthly basis, July and August had the highest numbers of boat launches (totals of 825 and 882, respectively).

The average number of boat launches per day generally showed an increase on weekends although from July to September there were increased numbers of launches on weekdays as well.

Throughout the year, the peak in boat launching took place in the morning between 6 am and 10 am.
 

Mean hourly boat launch rate per month at Entrance Point boat ramp, Broome, from November 2012 to October 2013.

“The results support the original hypothesis that there would be an increase in boat launches during the dry, winter season when there are known to be more visitors (especially ‘grey nomads’) to Broome,” project leader Murdoch University’s Professor Lynnath Beckley said. “However, consistent launching of boats during the wet, summer season (40 per cent of all launches) clearly indicates the importance the residents of Broome place on recreational boating.”

The boat launching data were also explored relative to environmental factors like air and sea temperature, wind speed and direction, rainfall, barometric pressure and tides as well as time of day, day type (weekday, weekend or public holiday) and school holidays.

Time series analyses of the hourly launch data showed that day type, time of day, school holidays and tidal height were significant predictors that together described the most variation in the launches on a daily cycle.  For the weekly cycle, only day type and wind speed were significant predictors.

“The Entrance Point boat ramp is only one of several sites from where recreational boats are launched in Broome and this may have some bearing on the patterns found,” Professor Beckley said. “For example, during the winter mornings when there can be strong easterly winds, many boats are launched instead from the southern end of Cable Beach which is more protected from these winds.”

Entrance Point boat ramp at Broome in peak season (Lynnath Beckley)

 

The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley.

Category: 

Kimberley Marine Research Program

Broome boat ramp study indicates boating popularity

/in , /by

Researchers have analysed a year’s worth of video imagery from the popular Entrance Point boat ramp, adjacent to the Broome Fishing Club, to explore the factors affecting the launching of recreational boats, as part of a broader WAMSI study looking at Human Use in the Kimberley.

In total, 6057 recreational boat launches were recorded by the Western Australian Department of Fisheries camera at Entrance Point during the 12 month study. The figure shows that, despite the town of Broome only having a relatively small resident population of about 13,000 people, boating is a popular activity.

To put it into context, the total at Entrance Point is equivalent to about 22 per cent of the total number of launches per year at Hillarys boat ramp which is one of the busiest in the Perth Metropolitan area.

On a seasonal basis, 60 per cent of all boat launches at Entrance Point occurred during the dry, winter season (May to October) and on a monthly basis, July and August had the highest numbers of boat launches (totals of 825 and 882, respectively).

The average number of boat launches per day generally showed an increase on weekends although from July to September there were increased numbers of launches on weekdays as well.

Throughout the year, the peak in boat launching took place in the morning between 6 am and 10 am.

Mean hourly boat launch rate per month at Entrance Point boat ramp, Broome, from November 2012 to October 2013.

“The results support the original hypothesis that there would be an increase in boat launches during the dry, winter season when there are known to be more visitors (especially ‘grey nomads’) to Broome,” project leader Murdoch University’s Professor Lynnath Beckley said. “However, consistent launching of boats during the wet, summer season (40 per cent of all launches) clearly indicates the importance the residents of Broome place on recreational boating.”

The boat launching data were also explored relative to environmental factors like air and sea temperature, wind speed and direction, rainfall, barometric pressure and tides as well as time of day, day type (weekday, weekend or public holiday) and school holidays.

Time series analyses of the hourly launch data showed that day type, time of day, school holidays and tidal height were significant predictors that together described the most variation in the launches on a daily cycle.  For the weekly cycle, only day type and wind speed were significant predictors.

“The Entrance Point boat ramp is only one of several sites from where recreational boats are launched in Broome and this may have some bearing on the patterns found,” Professor Beckley said. “For example, during the winter mornings when there can be strong easterly winds, many boats are launched instead from the southern end of Cable Beach which is more protected from these winds.”

Entrance Point boat ramp at Broome in peak season (Lynnath Beckley)

The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley.

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Kimberley Marine Research Program

IMOS to drive fresh future for marine priorities in the west

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WAMSI welcomed the Commonwealth’s announcement that provides funding certainty for the National Collaborative Research Infrastructure (NCRIS) program. The NCRIS created and developed the Integrated Marine Observing System (IMOS) and the $1.5 billion commitment over the next decade gives IMOS a guaranteed share, and a green light to make plans for the future.

Associate Professor Julian Partridge is the new Western Australian IMOS (WAIMOS) node leader, responsible for advising the national program on regional priorities and directions for investment.

Associate Professor Julian Partridge, CEO WA-IMOS

With the launch last year of Western Australia’s Blueprint for Marine Science priorities, backed by the National Marine Science Plan, WAIMOS has strong benchmarks to draw on to drive the State’s marine observing priorities, including strongly advocated research collaborations and data sharing.   

“A focus for the coming months will include the review of priorities for deployment off the western coast of Australia,” Associate Professor Partridge said. “With the welcome new lease of life from the NCRIS decisions, we have the chance to take stock and make sure we’re measuring the most important things. In addition, we need to maximize the value of WAIMOS data to a variety of stakeholders and end users; and we need to consider our activities in the light of both impact and innovation agendas.”

IMOS has produced data that has enabled the development of a wide range of regional models that improve the understanding of both local and distant ocean currents and processes, which have supported both private and public management and policy decisions.

WAMSI will continue to support the WAIMOS node and take steps to connect it into the continuing Blueprint process to improve the input from industry, government and consultants to the framework and priorities for IMOS.

“We have a relatively short timeline to develop priorities for the next five years of IMOS investment,” WAMSI CEO Patrick Seares said. “However, we are fortunate in Western Australia that we have both worlds: an end-user led Blueprint for Marine Science 2050 report explicitly outlining industry and government priorities for new information; and a National Marine Science Plan containing expert and in-depth analysis of what research and capability is required. These processes plus the more recent Forum for Operational Oceanography allow us to ensure we are advising IMOS to invest in the most valuable observations off our coast, safe in the knowledge we’re meeting the priorities for both research and end-users.”

That sinking feeling: Suspended sediments can prevent the ascent of coral egg bundles

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New research has demonstrated a previously unrecognised event that can markedly reduce the probability that coral gametes (egg-sperm bundels) reach the water surface and come in contact with each other.

Inshore reefs are regularly exposed to higher concentrations of suspended sediments during storms, runoff and dredging. While it has been recognised that suspended sediments can negatively impact fertilisation and later life cycle stages, the vulnerability of the egg-sperm bundles during their journey to the water’s surface has not been considered.

Lead author of the WAMSI research published in Scientific Reports Gerard Ricardo (AIMS/UWA) explained many corals reproduce through synchronised broadcast spawning of gametes and the buoyancy of egg-sperm bundles is critical to fertilisation at the ocean surface.

“We demonstrated that during their ascent to the surface, the egg-sperm bundles can run into suspended sediment grains that stick to their mucous coating, and that under certain water quality conditions the sediment grains are enough to cause a significant number of bundles to sink and never reach the water surface, or be slowed in their ascent” Gerard said.

A coral colony releases egg-sperm bundles into the water column. (G. Ricardo)

The detrimental effect this has on the reproduction of corals is made worse by the fact that the bundles carry both eggs and sperm and the bundles need to reach the water surface and break apart for fertilisation to occur. So if less bundles make it to the surface, the coral spawn slick will be less concentrated and therefore there is less chance two compatible gametes will bump into each other.

“Even if the egg-sperm bundles do make it to the surface, they may arrive too late and miss the party; as wind, waves and currents can quickly dilute and disperse a coral spawn slick,” Gerard explained.

Microscopy image of a coral egg-sperm bundle after failed ascent through elevated concentrations of suspended sediments, revealing considerable attachment of sediment grains (yellow) to the bundles (purple). (Gerard Ricardo)

The observations were captured using a mathematical model that predicts the reduction in ascent probability and egg-sperm encounters as a function of sediment load, depth and particle grain size.

For reefs at 15 metres deep, the model predicts that a coarse silt could reduce 10 per cent of egg-sperm encounters at suspended sediment concentrations of 35 milligrams per litre, and for a reef at 5 metres deep, it could reduce 10% of the encounters at 105 milligrams per litre.

“This is the first study to examine the effects of environmental pressures on the success of coral gamete ascent, which can have important flow-on effects for the ability of a reef to maintain and recover its population,” Gerard said. “It adds to the list of stressors impacting early life history stages of corals and could prevent new corals from adding to the population on nearby reefs.”

It’s thought the mechanism and model used in this research could also be used to determine the effects of sediment grains on the reproductive success of other marine organisms that rely on positively buoyant eggs for fertilisation including some echinoderms, molluscs and fish.

Gerard Ricardo and researchers in the lab A microscopy image of an egg-sperm bundle showing eggs (orange) and sperm (white). (G. Ricardo)

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The WAMSI Dredging Science Node is made possible through $9.5 million invested by Woodside, Chevron and BHP as environmental offsets. A further $9.5 million has been co-invested by the WAMSI Joint Venture partners, adding significantly more value to this initial industry investment. The node is also supported through critical data provided by Chevron, Woodside and Rio Tinto Iron Ore.

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Dredging Science

New type of reef identified in the Kimberley

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The remote Kimberley coast is characterised by its extreme tidal ranges, warm turbid waters and frequent cyclonic events, and is also home to a newly recognised form of coral reef, one which grows higher than any other reef type in the world.

Curtin University researcher Dr Mick O’Leary has been leading a Western Australian Marine Science Institution (WAMSI) project team that’s been characterising the surface morphology and internal architecture of Kimberley coral reefs using mutlibeam sonar and seismic profiling technologies, as well as collecting reef cores to establish growth histories and ecological change on thousand year time scales.

The findings, published in the journal Coral Reefs, provide new insights into the ability of Kimberley corals to survive, endure, and thrive, in what is generally considered to be environmentally challenging conditions for coral growth.

The seismic profiling revealed that the living coral veneer does not represent simple coral communities growing on rock foundations but are in fact the surface expression of massive and complex reef structures comparable to what we might see at Ningaloo or the Abrolhos or even the Great Barrier Reef.

Percussion coring on Bathurst-Irvine Island, core length up to six metres were recovered using this method. (Mick O’Leary)

The research team drove 6.5 metre lengths of aluminium tubing into the reef structure to recover a record of reef growth. Radiocarbon dating of corals collected from reef cores revealed that coral growth commenced in the Kimberley almost immediately after the continental shelf was flooded by rising sea levels that followed the end of the last ice age some 12 to 15 thousand years ago, with the oldest dated inshore corals returning ages of more than 9000 years.

The most unusual feature of Kimberley reefs is the elevation of their reef flats. Typically coral reefs will grow vertically until they reach sea level, then having used up all the available vertical space, they switch growth directions and begin to grow laterally into deeper water. The upper vertical limit of reef growth is the mean low water tide level, as corals can only tolerate exposure to the atmosphere for brief periods, which usually occurs around spring low tides.

However, the team’s multibeam sonar surveys have precisely measured the elevation of the reef flats and revealed that Kimberley reefs have grown vertically through the mean low water level limit up to the mean tide level.

“This basically means the corals on the reef flat spend half their life exposed above the level of the tide,” Dr O’Leary said. “The sight of water cascading off the edges of a Kimberley coral reef as the tide falls is something that you can experience nowhere else on Earth.”

Somehow Kimberley corals have managed to adapt over many thousands of years to these extreme tidal ranges, high levels of turbidity, really warm water temperatures and exposure, and are thriving in the Kimberley despite these conditions.

So as we see the beginnings of yet another major bleaching event on the Great Barrier Reef, we might look to these more robust Kimberley coral reefs and ask what is unique about these corals? How long did it take to adapt to the unique Kimberley marine environments and are there lessons here that can be applied to the more sensitive coral reef regions of the world?

Water cascading off the reef at Tallon Island (Tubagus Solihuddin)

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The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley.

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Kimberley Marine Research Program

River Release | 9 News Perth

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New life is being breathed into Perth’s waterways with 400 thousand juvenile prawns being released into the Canning River. The restocking program has been running for the past four years, rejuvenating a dying hobby and getting families back on the water.

Government Media Statement: Four millionth prawn for Swan and Canning rivers

 

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Estuary Science

Science maximises prawn restocking success

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Estuary Science