What is a detention?
The IMO defines a detention as: ‘intervention action taken by the port State when the condition of the ship or its crew does not correspond substantially with the applicable conventions to ensure that the ship will not sail until it can proceed to sea without presenting a danger to the ship or persons on board, or without presenting an unreasonable threat of harm to the marine environment, whether or not such action will affect the scheduled departure of the ship’.
Detainable deficiencies by category
Table 11 shows the proportion of detainable deficiencies in different categories over a three-year period. As indicated in the table, the detainable deficiencies relating to the category of ISM remained the highest, though decreasing in share in 2021 (24 per cent of detainable deficiencies) as compared to 2020 (28.1 per cent of detainable deficiencies). Along with ISM, the categories of fire safety, emergency systems, lifesaving appliances and water/weather-tight conditions were the top five categories of detainable deficiencies. The proportion of MLC-related detentions remained the 7th highest category. AMSA exercised flexibility and worked with industry in its dealings with MLC related deficiencies during the height of the COVID-19 pandemic. Flexibility and proactive work with industry, specifically around seafarer repatriation, prevented a significant surge in detainable deficiencies relating to MLC.
The relatively high proportion of detainable deficiencies attributed in the ISM category suggests that safety management systems (SMS) are not properly and effectively implemented onboard. While the proportion may be a cause of concern, history provides context. In 2013, the number of ISM detainable deficiencies peaked at 120 (31.2 per cent share of detainable deficiencies). While there was an increase in ISM deficiencies between 2018-2020, the decrease in ISM deficiencies between 2020 (28.1%) and 2021(24%) is a positive result.
Shipboard operations and maintenance were again the highest contributors to ISM detentions, followed by emergency preparedness.
Table 11 – Detainable deficiencies by category
No. of deficiencies
|Certificates and documentation||3||1.1%||6||2.7%||↑|
|Cargo operations including equipment||5||1.9%||4||1.8%||↓|
|Safety of navigation||0||0.0%||4||1.8%||↑|
|Propulsion and auxiliary machinery||1||0.4%||2||0.9%||↑|
Detentions by ship type
In 2021 AMSA detained 159 ships with an average detention rate of 5.6 per cent compared to 178 ships detained in 2020 with an average detention rate of 5.9 per cent.
Table 12 – Top five detention rates by ship type in 2020 and 2021
|AMSA detained 159 ships in 2021, with an average detention rate of 5.6%.||2020 – 5.9% average (number of detentions)||2021 – 5.6% average (number of detentions)|
|General cargo/multi-purpose ship –– 10.4% (14)||Heavy load carrier – 14.8% (4)|
|Heavy load carrier – 8.3% (3)||General cargo/multi-purpose ship – 7.7% (12)|
|Livestock carrier – 6.9% (2)||Container ship –– 7.6% (18)|
|Bulk carrier – 6.6% (121)||Oil tanker/chemical tanker – 6.3% (1)|
|Container ship – 6.5% (17)||Bulk carrier – 6.1% (105)|
Note: only ship types with 10 or more inspections are included.
The poorest performing ship type was heavy load carriers, followed by general cargo ships and container ships. General cargo ships have been in the top five poorest performing ship types for the past eight years while container ships have been in the top five for the past four years.
Bulk carriers represented the largest number of PSC detentions, as shown in Table 13. The bulk carrier detention rate was 6.1 per cent, and this detention rate remains higher than the average detention rate. This is a continuing and concerning trend as bulk carriers have exceeded the average detention rate for the last six years and are among the five worst performing ship types again in 2021, while also being the highest proportion of ship arrivals4.
Table 13 – Detentions by ship type
|Ship type||Inspections||Detentions||Detention rate||Detention rate|
|general cargo/multi-purpose ship||156||12||7.7%||10.4%|
|heavy load carrier||27||4||14.8%||8.3%|
|offshore service vessel||10||0||0.0%||0.0%|
|oil tanker/chemical tanker||16||1||6.3%||0.0%|
|oil tanker/NLS tanker||1*||0||0.0%||0.0%|
|other types of ship||26||0||0.0%||0.0%|
|refrigerated cargo vessel||4*||1||25.0%||0.0%|
|ro-ro cargo ship||4*||1||25.0%||0.0%|
|special purpose ship||5*||0||0.0%||0.0%|
* As there are less than 10 inspections of this ship type these are not counted in the deficiency rate performance assessment.
The following is notable with regard to detention by ship type in 2021:
- 1,712 bulk carriers were inspected with 4,051 deficiencies issued resulting in 105 detentions. The detention rate for bulk carriers decreased to 6.1% from 6.6% in 2020.
- Heavy load carriers had the highest detention rate at 14.8%, a 6.5% increase compared to 8.3% in 2020.
- General cargo vessels had the second highest detention rate at 7.7%, a 2.7% decrease compared to 2020.
- General cargo ships and heavy load carriers had the two highest detention rates of all ship types in 2021, 2020 and 2019.
- Oil tankers had a detention rate of 1.6%, well below the 2021 average of 5.6%.
- Offshore service vessels had zero detentions from 10 inspections.
- Tugboats had one detention from 18 inspections.
Detentions by flag State
Individual flag State performance can be determined by comparing the percentage share of inspections against the percentage share of detentions for each flag State (as shown in figure 4 below). Below average performance is indicated when a flag State’s percentage share of detentions is higher than its percentage share of inspections.
Top five detention rates by flag State 2021
There was a total of 159 foreign-flag ships detained in 2021.
The average detention rate for all ships was 5.6%.
|Flag State (Detention Rate %)|
|1. Antigua and Barbuda – 11.1%|
|2. Denmark – 10.0%|
|3. Taiwan (Province of China) – 10.0%|
|4. Thailand – 10.0%|
|5. Portugal – 8.8%|
Note: this table only covers ship types with 10 or more inspections.
Where a flag State is subject to a small number of inspections, a single detention can result in the flag State exceeding the average detention rate, as shown in Table 15. This may not be an accurate measure of performance. A more accurate assessment of individual flag State performance can be drawn by comparing detention rates over three years as shown in Table 14. This table shows that Antigua and Barbuda, Denmark, Greece, Liberia and Panama have exceeded the overall average detention rate over the three years from 2019 to 2021.
Table 14 – Flag States that exceeded the average in 2019, 2020 and 2021
|2019 (average 5.1%)||2020 (average 5.9%)||2021 (average 5.6%)|
|Flag State||Detention rate
|Flag State||Detention rate
|Flag State||Detention rate
|Antigua and Barbuda||13.3% (4)||Denmark||16.7% (2)||Antigua and Barbuda||11.1% (4)|
|Cayman Islands||10.3% (3)||Antigua and Barbuda||10.8% (4)||Denmark||10.0% (1)|
|Cyprus||9.1% (6)||Taiwan (Province of China)||10.0% (1)||Taiwan (Province of China)||10.0% (1)|
|Philippines||9.1% (1)||Norway||9.1% (5)||Thailand||10.0% (1)|
|Denmark||8.3% (2)||Netherlands||8.7% (2)||Portugal||8.8% (3)|
|Malaysia||8.3% (1)||Liberia||8.0% (32)||Panama||7.2% (45)|
|Liberia||6.7% (27)||Panama||6.7% (47)||Greece||7.1% (3)|
|Greece||6.3% (4)||Hong Kong, China||6.7% (22)||Netherlands||7.1% (1)|
|Panama||6.3% (43)||Greece||6.4% (3)||Liberia||6.6% (25)|
|Luxembourg||6.3% (1)||Marshall Islands||6.5% (28)|
|Malta||5.8% (11)||United Kingdom||6.3% (1)|
|Isle of Man||5.6% (3)||Hong Kong, China||5.9% (21)|
Bold text = Exceeded the average detention rate in two years out of three
Italics = Exceeded the average detention rate in three years out of three
Table 15 – Inspections and detentions by flag State
|Flag State||Inspections||Detentions||Detention rate|
|ANTIGUA & BARBUDA||36||4||11.1%|
|HONG KONG, CHINA||358||21||5.9%|
|ISLE OF MAN||42||1||2.4%|
|KOREA (THE REPUBLIC OF)||23||0||0.0%|
|TAIWAN (PROVINCE OF CHINA)||10||1||10.0%|
|UNITED STATES OF AMERICA||2||0||0.0%|
Note: flag States above the average detention rate with more than 10 inspections are provided in bold.
Figure 4 – Share of detentions compared to share of inspections
Note: a detailed breakdown of this graph can be found in the Appendix.
4 All foreign flag ships are eligible for inspection six months from a previous inspection by AMSA or on their first arrival at an Australian port.