Frequency of monitoring

Research and monitoring

Introduction

The object of monitoring is to obtain a measure of the health of a population, ecosystem or the impact of an action such as protection. In the case of marine mammals, monitoring frequency should allow a representative measure of abundance or habitat usage. Monitoring frequency depends on factors including the goal of the monitoring programme and the availability of resources. It also depends on whether a species is migratory, sedentary, or uses local different local habitats throughout the year.

Mammals ©Kimberly Jeffries

Migratory species

If migratory species travel throughout, within or between the MPA(s) on an annual migration, then there is little need to monitor at other times. Therefore, Humpback whales in South-east Queensland, for example, need only be monitored for the period during which they are traversing the region [1]. Regular annual surveys are preferable to less-frequent monitoring, as some species may exhibit natural inter-annual variability. For example, the distribution of some cetacean species have been known to change in El Nino years [2].

Resident species

Resident marine mammal species often reside in the one area, but many species show a variety of movement behaviours at a location. For example, around Tenerife, in the Canary Islands, some short-finned pilot whales are resident, some undergo small-scale migrations, and some are thought to be transient [3]. Therefore, the monitoring frequency should reflect the goal of the monitoring. If the purpose of the monitoring is to generate an absolute or relative census, then once per year or every two years may be sufficient. However, where monitoring relates to, for example, habitat use over time, or developing an understanding of subpopulations, multiple surveys may be required each year.

Physical parameters

Physical oceanographic monitoring (depending on the particular parameter) can be measured in different ways, from satellite imagery to moored buoys, to boat-based sampling. Most of these parameters vary throughout the year and are likely to vary from week to week as a result of weather events. Therefore, weekly, monthly or quarter-annually monitoring is preferable where resources and available skills permit [4].

Case study

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Resources
& references

[1] Noad, M.J., Dunlop, R.A., Paton, D. and Cato, D.H. 2008. Unpublished report, An update of the east Australian humpback whale population (E1) rate of increase, International Whaling Commission Scientific Committee, Santiago, Chile.
[2] Dawson S., Wade P., Slooten E. and Barlow J. 2008. Design and field methods for sighting surveys of cetaceans in coastal and riverine habitats. Mammal Review 38 (1): 19–49
[3] Servidio A, Pérez-Gil E, Pérez-Gil M,Cañadas A, Hammond PS, Martín V. Site fidelity and move-ment patterns of short-finned pilot whales within the CanaryIslands: Evidence for resident and transient populations.Aquatic Conserv: Mar Freshw Ecosyst. 2019;29(S1):227–241.
[4] Pomeroy R.S., Parks J.E., Watson L.M. 2004. How is your MPA doing? A guidebook of natural and social indicators for evaluating marine protected area management effectiveness. IUCN, Gland, Switzerland and Cambridge, UK. 234 pp

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