Port sampling

Summary

Over the last 10 years, the Caribbean Netherlands fisheries on Saba and St. Eustatius have been monitored and multiple assessment reports have been made by Wageningen Marine Research (WMR) in collaboration with local Data Monitoring Officers (DMOs). However, due to challenges in collecting the necessary data, there are gaps in the data which can lead to large uncertainties in the current stock assessments and make it difficult to deliver a more detailed assessment of the fisheries and the state of the stocks.

The specific objectives of this report were to present the data challenges and provide recommendations to address the shortcomings in the current data collection. By addressing these and providing solutions, improvements of the Caribbean Netherlands fisheries monitoring program can be made.

The main gaps identified in the data are:

- Limited coverage by the logbook data, especially the case in St. Eustatius. This implies that large raising factors are applied when estimating total effort and landing estimates, which leads to more uncertain estimates.

- Landings not reported by species (at least for the main species) and port sampling for species composition not frequent enough to be able to produce landing estimates and abundance indices at the species level (instead of species groups). For instance in Saba, the number of trips sampled to estimate the length-composition of the landings was on average 60 per year (excluding 2011), with mainly lobster and redfish trips being sampled. On average, around 40 trips per year were sampled for species composition, taken representatively from the different fishing methods. This is less than one catch sampled per week. This is too low and needs to be intensified if data availability and quality are to improve.

- While some species are over-sampled for length-composition, others are not sampled enough to be able to compute reliable length-based indicators.

Our key recommendations are:

o Port sampling and biological data collection-frequency must be stepped up to meet minimum targets.

o Going along with fishers on the vessels, in order to measure catches on location. (Then fishermen won’t have to wait at the harbor for the DMOs work to be done.)

o Facilitate working in morning/midday/evening shifts. This enables data collection after regular working hours, e.g. when fishers come home late in the day (5-6pm).

o Set quantitative targets for data collection. We suggest targeting for a minimum of 70% logbook declarations, activity surveys, catch species composition and weight data (tonnes), while doubling the effort on selected species of importance

o Data collection will now need to include exact biometric data to establish length-weight and fecundity curves, sex ratios and reproductive seasons for individual species, as well as the collection of otoliths from a range of sizes for each species as a basis for age and growth studies by the WMR otolith lab.

o Have DMOs sit in a workspace with a clear view of the harbor where fishers arrive with their catches, so they can immediately act when boats arrive with their catches. This is mainly an issue for the St. Eustatius DMO.

o For bycatch measurements photographing the fish on a cm grid surface can save measuring time in port or on vessels. o Increase willingness of fishers to participate in data collection. o Incentivize fishers to participate by organizing regular (bimonthly or quarterly) gettogethers where the DMOs update fishers on some monitoring results, providing snacks and drinks.

o Provide dedicated freezer storage space for fishers at the harbor, enabling DMOs more time for the port sampling. Fishers willingness to wait for port sampling is understandably limited. By providing dedicated freezer storage facility, the DMOs can take extra time needed for sufficient biological sampling (i.e. species composition, length, sex) while the catch of the fishers stays fresh. The same can be done for lobster catches if a port-based holding area is provided. 

o Provide modern technologies to the fishers and/or DMOs, e.g. Electronic Reporting Systems (ERS) such as electronic logbooks, and GPS systems such as the Vessel Monitoring System (VMS).

o Arrange for closer involvement of WMR in work planning for the island DMO’s

Knowledge on the density, distribution and occurrence of whales and dolphins in the Caribbean Netherlands is sparse. This knowledge is needed as basic input for conservation and management of cetaceans in the area. Especially in the long term, dedicated data is needed to provide a base-line for monitoring the effect of policy decisions, such as a proposed implementation of a whale sanctuary.

Until recently, knowledge was mainly based on strandings and opportunistic sightings of whales and dolphins. Dedicated data collection, such as obtained from designed aerial or shipboard surveys, will provide reliable and unbiased estimates of abundances and describe distribution patterns and habitat use. However, these types of studies are costly. To explore options on how to bridge the gap between costs (high-low) and data quality (high-low), we investigated a method that could potentially provide long term and cost effective, albeit low quality (in certain aspects), data. In this report we present the results obtained using a port sampling programme used to monitor the fisheries of Saba, St. Eustatius and Bonaire.
During port sampling fishermen were interviewed after returning to the harbour from a fishing trip. The fishermen described their fishing activities and in addition they reported any sightings of whales or dolphins. The study on Saba has included the recording of cetacean sightings since July 2012, the same method has been applied in St. Eustatius since November 2012 and on Bonaire since January 2014. In total 59 different fishing vessels participated in the study (9 Saba, 15 St. Eustatius and 35 Bonaire). The waters around each island were divided into sub-areas to provide data on where the fishing effort took place and where sightings were made. Effort was described as "fishing trips" per sub-area, per month and per island. A total of 1428 days at sea were monitored, with 1020 from Saba, 292 from St. Eustatius and 116 from Bonaire.
During the study a total of 42 whale sightings of 71 individuals was made, of these 36 (62 animals) were recorded in Saba, 2 (2 animals) in St. Eustatius and 4 (4 animals) in Bonaire. There were 93 dolphin sightings consisting of 1362 individual animals. Of these, from Saba there were 71 sightings (877 animals), from St Eustatius 3 sightings (144 animals) and from Bonaire 19 sightings (341 animals).
The relative density (sightings per "fishing trip") showed a pronounced difference in occurrence of cetaceans between islands. The highest relative density of dolphins was found in Bonaire with 0.16 dolphin sightings/fishing trip. The highest relative density of whales was found in Saba with 0.04 whales/fishing trip. Occurrence of whales and dolphins indicated seasonal patterns, in particular for Saba waters where the monitoring ran for several years and most whale and dolphin sightings were in March. The spatial distribution in the Saba study area indicated that dolphins occur regularly on the Saba Bank. In Bonaire the data indicated that an area on the west side of the island and close to shore (<1 km) with high fishing effort also had a high occurrence of cetacean sightings.
An evaluation of the method used indicated that the sampling methodology could be adapted to improve data quality. Most important hereby is a standardization of data collection and data storage between the islands. It also showed that the information provided by the fishermen is very useful in identifying areas of research needed to further investigate cetacean distributional patterns and habitat use around these three islands.
This research was performed within EZ-program Beleidsondersteunend Onderzoek (BO). BO-11-011.05- 034, BO-11-011-05-008.