diff --git a/backend/project/api/serializers/observations.py b/backend/project/api/serializers/observations.py
index 38f0925..d5e0da6 100644
--- a/backend/project/api/serializers/observations.py
+++ b/backend/project/api/serializers/observations.py
@@ -38,12 +38,12 @@ class ThumbnailSerializer(serializers.Serializer):
     large = serializers.SerializerMethodField()
 
     def get_thumbnail_by_size(
-        self, obj, height=100, width=100, format="JPG", quality=70
+        self, obj, height=100, width=100, format="JPEG", quality=70
     ):
         if obj.media_type == Media.MediaType.IMAGE:
             return self.context["request"].build_absolute_uri(
                 get_thumbnail(
-                    obj.media_file, f"{height}x{width}", format=format, quality=quality
+                    obj.media_file, f"{width}x{height}", format=format, quality=quality
                 ).url
             )
         return None
@@ -69,12 +69,11 @@ class Meta:
         fields = ("id", "uuid", "legend", "media_file", "media_type", "thumbnails")
 
 
-class ObservationListSerializer(
-    DynamicFieldsMixin, gis_serializers.GeoFeatureModelSerializer
-):
+class ObservationMixin(DynamicFieldsMixin, gis_serializers.GeoFeatureModelSerializer):
     source = serializers.SlugRelatedField("label", read_only=True)
-    subtype = serializers.SlugRelatedField("label", read_only=True)
-    # event_type = serializers.SlugRelatedField("event_subtype.event_type.label", read_only=True)
+    subtype = serializers.SlugRelatedField(
+        "label", source="observation_subtype", read_only=True
+    )
 
     class Meta:
         model = Observation
@@ -86,14 +85,19 @@ class Meta:
             "event_date",
             "source",
             "subtype",
-            "observation_subtype",
-            "location",
         )
         write_only_fields = ("observation_subtype__id",)
 
 
-class ObservationDetailSerializer(ObservationListSerializer):
+class ObservationListSerializer(ObservationMixin):
+    first_photo = MediaSerializer(read_only=True)
+
+    class Meta(ObservationMixin.Meta):
+        fields = ObservationMixin.Meta.fields + ("first_photo",)
+
+
+class ObservationDetailSerializer(ObservationMixin):
     medias = MediaSerializer(many=True, read_only=True)
 
-    class Meta(ObservationListSerializer.Meta):
-        fields = ObservationListSerializer.Meta.fields + ("medias",)
+    class Meta(ObservationMixin.Meta):
+        fields = ObservationMixin.Meta.fields + ("medias",)
diff --git a/backend/project/api/views.py b/backend/project/api/views.py
index a15e6de..ac9d1dd 100644
--- a/backend/project/api/views.py
+++ b/backend/project/api/views.py
@@ -40,8 +40,10 @@ def get(self, request):
 
 
 class ObservationViewSet(viewsets.ReadOnlyModelViewSet):
-    queryset = Observation.objects.all().select_related(
-        "source", "observation_subtype__observation_type"
+    queryset = (
+        Observation.objects.all()
+        .select_related("source", "observation_subtype__observation_type")
+        .prefetch_related("medias")
     )
     filter_backends = (DjangoFilterBackend,)
     filterset_class = ObservationFilterSet
@@ -79,7 +81,11 @@ class AccountObservationViewset(viewsets.ModelViewSet):
     permission_classes = [permissions.IsAuthenticated]
 
     def get_queryset(self):
-        return self.request.user.observations.all()
+        return (
+            self.request.user.observations.all()
+            .select_related("source", "observation_subtype__observation_type")
+            .prefetch_related("medias")
+        )
 
     def get_serializer_class(self):
         if self.action == "list":
diff --git a/backend/project/observations/models.py b/backend/project/observations/models.py
index 6f2ed7d..27d37c9 100644
--- a/backend/project/observations/models.py
+++ b/backend/project/observations/models.py
@@ -68,6 +68,10 @@ class Observation(TimeStampMixin):
     )
     location = models.PointField(srid=4326, verbose_name=_("Location"))
 
+    @property
+    def first_photo(self):
+        return self.medias.first()
+
     def __str__(self):
         return str(self.uuid)